updated competent persons` report on the mineral assets of broken

Transcription

87 Colin Street West Perth WA 6005
PO Box 77 West Perth WA 6872
Telephone +61 8 9213 9213
Facsimile +61 8 9322 2576
[email protected]
www.snowdengroup.com
Perth, Brisbane, Vancouver, Johannesburg, London
29 October 2007
The Directors
Broken Hill Cobalt Ltd
Level 2, 160 Pitt St Mall
SYDNEY NSW 2000
Dear Sirs
UPDATED COMPETENT PERSONS’ REPORT ON THE
MINERAL ASSETS OF BROKEN HILL COBALT LIMITED
At your request (agreement dated 9 July 2007) Snowden Mining Industry Consultants Pty Ltd
(“Snowden”) has prepared an update of its February 2005 Competent Persons’ Report on the Mineral
Assets of Broken Hill Cobalt Ltd (“BHCL”) located in the Broken Hill region of New South Wales. It is
our understanding that this report is to be used in support of BHCL’s listing on the Australian Securities
Exchange (“ASX”). The purpose of the Prospectus is to offer for subscription 25 M ordinary shares at
an issue price of $0.20 to raise a total of $5 M before costs of the issue to fund the future assessments
of BHCL’s projects. There is also the facility for an over subscription of up to 10 M shares to raise an
additional $2 M.
BHCL is an unlisted public company which was incorporated in New Zealand in 1988. BHCL is
currently 33% owned by Heritage Gold (New Zealand) Ltd (“Heritage”) and 67% owned by So Co Ltd
(“SoCo”).
BCHL’s mineral assets comprise a 100% interest in the Thackaringa and Pine Ridge projects located
near the historic mining centre of Broken Hill in western New South Wales.
The objective of this report is to present for both projects a geological description, an outline of
previous exploration and evaluation studies, an opinion on the potential of the projects and on the
proposed costed exploration and development programmes for the next two years.
Snowden has based its assessment of BHCL’s project tenements on a site visit to the Broken Hill
project areas during January 2005, discussions with the directors and senior management of BHCL
and their technical advisors, and on technical information compiled by BCHL and previous tenement
holders.
A listing of the documents referenced is provided at the end of this report. Consents have been sought
from BHCL’s management and consultants to include technical information and opinions expressed by
them. None of the other entities referred to in this report have consented to their inclusion and have
only been referred to in the context of reporting material fact.
Snowden has based its findings upon information known to us at 29 October 2007 and has satisfied
itself that all material information in the possession of BHCL has been fully disclosed to Snowden. A
draft version of this report was provided to the directors of BHCL for comment in respect of omission
and factual accuracy.
Snowden has prepared this report on the understanding that all BHCL’s mineral tenements are
currently in good standing. Snowden has not investigated the current ownership status and standing
Snowden Mining Industry Consultants Pty Ltd ABN 99 085 319 562
SNOWDEN IS A SUBSIDIARY OF DOWNER EDI LIMITED
071030_Final_7020_BHCL_CPR.doc
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of BHCL’s mineral rights within each of its project areas and is not qualified to make legal
representations in this regard. It is our understanding that this matter has been dealt with in a
separate report provided by Australian Mining Title Services.
The proposed exploration and feasibility programmes developed by the management of BHCL and
reviewed by Snowden have been designed to realise the potential of the projects in a rational and
efficient manner. The budgeted work programmes currently planned by BHCL for its project areas and
management costs amount to $3.62 M. We note that the company will have sufficient working capital
to carry out its stated objectives if the share issue to raise $5 M upon listing is fully subscribed.
From Snowden’s assessment of BHCL’s principal projects at Thackaringa and Pine Ridge in the
Broken Hill district, it is our opinion that the projects are of merit and that the evaluation programmes
proposed have been carefully conceived and costed.
This report has been prepared in accordance with the Code for the Technical Assessment and
Valuation of Mineral and Petroleum Assets and Securities for Independent Experts Reports (“the
VALMIN Code”) and the Australasian Code for Reporting of Exploration Results, Mineral Resources
and Ore Reserves (“the JORC Code”). The Snowden personnel responsible for the compilation and
review of this report are:
Mr Jason Froud, BSc (Hons), Grad Dip (App Fin), MAusIMM – Senior Consultant;
Mr Michael Tyndall, BSc (Hons), Grad Dip (Min Eng), MAusIMM – Principal Consultant;
Mr Peter Myers, BEng (Mining) (Hons), MAusIMM – Principal Consultant Engineer; and
Mr Peter Munro, BAppSc, BCom, MAusIMM – Senior Principal Consulting Engineer.
Snowden Mining Industry Consultants Pty Ltd is an independent firm providing specialist mining
industry consultancy services in the fields of geology, exploration, resource estimation, mining
engineering, geotechnical engineering, risk assessment, mining information technology and corporate
services. The company, with its principal office at 87 Colin Street, West Perth, Australia, also operates
from offices in Brisbane, Johannesburg, Cape Town, Vancouver, Belo Horizonte and London and has
prepared independent expert reports and valuations on a variety of mineral commodities in many
countries.
Neither Snowden nor those involved in the preparation of this report have any material interest in
BHCL or in the mineral properties considered in this report. Snowden is remunerated for this report by
way of a professional fee determined according to a standard schedule of rates which is not contingent
on the outcome of this report.
Snowden has given and has not before lodgement of the BHCL’s Prospectus withdrawn its written
consent to being named as author of this report and to the inclusion of this report in its Prospectus.
Yours faithfully
Mr J C Froud
Mr M C Tyndall
BSc (Hons), Grad Dip (App Fin), MAusIMM
BSc (Hons), Grad Dip (Min Eng), MAusIMM
Senior Consultant – Corporate Services
Principal Consultant – Corporate Services
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TABLE OF CONTENTS
SUMMARY ....................................................................................................................................5
INTRODUCTION...........................................................................................................................7
GEOLOGICAL OVERVIEW ..........................................................................................................8
THACKARINGA PROJECT ....................................................................................................... 10
4.1 INTRODUCTION ............................................................................................................ 10
4.2 PYRITE HILL .................................................................................................................. 11
4.3 BIG HILL ......................................................................................................................... 12
4.4 MINING AND EXPLORATION HISTORY ...................................................................... 13
4.5 MINERAL RESOURCE ESTIMATES ............................................................................. 13
4.5.1
Data collection ................................................................................................. 13
4.5.2
Assay and sample QA/QC .............................................................................. 17
4.5.3
Bulk density ..................................................................................................... 17
4.5.4
Geological interpretation ................................................................................. 18
4.5.5
Resource estimation ........................................................................................ 19
4.5.6
Resource classification .................................................................................... 19
4.6 MINING AND PROCESSING STUDIES ........................................................................ 20
4.7 DEVELOPMENT OPTIONS ........................................................................................... 21
4.8 REVIEW OF MINERALOGY AND PROCESSING ISSUES .......................................... 22
4.8.1
Mineralogy ....................................................................................................... 22
4.8.2
Concentration .................................................................................................. 22
4.8.3
Pyrite Oxidation ............................................................................................... 23
4.8.4
Leaching .......................................................................................................... 23
4.8.5
Purification ....................................................................................................... 24
4.8.6
Comparable operations ................................................................................... 25
4.8.7
Conclusion ....................................................................................................... 25
4.9 EXPLORATION POTENTIAL ......................................................................................... 26
4.10 PROPOSED PROGRAMME AND EXPENDITURE ....................................................... 26
5.
PINE RIDGE PROJECT ............................................................................................................ 27
5.1 INTRODUCTION ............................................................................................................ 27
5.1.1
North East Extensions ..................................................................................... 27
5.1.2
Himalaya North ................................................................................................ 28
5.1.3
Pyramid Hill ..................................................................................................... 29
5.1.4
Tower Hill ......................................................................................................... 29
5.1.5
Ram Paddock .................................................................................................. 29
5.1.6
Other areas ...................................................................................................... 29
5.2 EXPLORATION POTENTIAL ......................................................................................... 29
5.3 PROPOSED WORK PROGRAMME AND BUDGET ..................................................... 29
DECLARATIONS BY SNOWDEN MINING INDUSTRY CONSULTANTS ............................................ 30
INDEPENDENCE ...................................................................................................................... 30
QUALIFICATIONS .................................................................................................................... 30
BIBLIOGRAPHY .................................................................................................................................... 32
GLOSSARY OF TECHNICAL TERMS .................................................................................................. 35
SELECTED DRILLING RESULTS ......................................................................................................... 43
1.
2.
3.
4.
LIST OF TABLES
Table 1.1
Table 3.1
Table 4.1
Table 4.2
Table 4.3
Table 4.4
Table 5.1
Summary of BHCL’s work programme and budget ....................................................... 6
Tenement status for BHCL’s Curnamona Province projects ......................................... 9
Mining and exploration history at the Thackaringa and Pine Ridge projects ............... 15
Summary of drilling at the Thackaringa and Pine Ridge projects ................................ 16
Comparison of the Pyrite Hill resource estimates ........................................................ 19
Thackaringa project work programme budget ............................................................. 26
Pine Ridge project work programme and budget ......................................................... 30
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LIST OF FIGURES
Figure 2.1
Figure 3.1
Figure 4.1
Figure 4.2
Figure 4.3
Figure 4.4
Figure 4.5
Figure 4.6
Figure 4.7
Figure 5.1
Figure 5.2
Location plan of BHCL’s Broken Hill projects ................................................................ 8
Curnamona Craton geological plan................................................................................ 9
Thackaringa project geological plan............................................................................. 10
Geological plan of the Pyrite Hill deposit ..................................................................... 11
Typical cross section through the Pyrite Hill deposit.................................................... 12
Illustrative long section through the Pyrite Hill deposit................................................. 13
Geological plan of the Big Hill project .......................................................................... 14
Scatter plot of check assays for Pyrite Hill ................................................................... 17
Scatter plot of water immersion and downhole probe density determinations ............ 18
Location plan of exploration targets at the Pine Ridge project .................................... 27
Geological plan of the North East Extensions prospect ............................................... 28
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1.
SUMMARY
Broken Hill Cobalt Ltd (“BHCL”) is an unlisted public company incorporated in New Zealand in 1988
and is currently 33% owned by Heritage Gold (New Zealand) Ltd (“Heritage”) and 67% owned by So
Co Ltd (“SoCo”).
BHCL’s mineral assets comprise two Inferred cobalt Mineral Resources and exploration projects in the
Broken Hill mining district. The properties comprise a 100% holding in two mining leases (ML 86 and
87 – Thackaringa) and one exploration lease (EL6622 – Pine Ridge).
2
BHCL’s projects cover a total area of approximately 64 km , located some 20 km southwest of the city
of Broken Hill in the southeastern corner of the Proterozoic Curnamona Province. The Curnamona
Province is prodigiously mineralised and hosts the world class Broken Hill lead-zinc-silver deposit.
Previous mining and exploration activities in the Broken Hill district have focussed on areas of outcrop
or shallow cover and were largely concentrated on Broken Hill Type base metal mineralisation,
although considerable gold, tin, rare earth and industrial minerals exploration has also been recorded
from the district.
Despite BHCL’s current tenements having been explored on an intermittent basis since the discovery
of sulphide mineralisation at Broken Hill in the early 1880s, significant cobalt mineralisation was not
identified until the 1960s. BHCL’s Broken Hill project areas are known to host two large low grade
cobaltiferous pyrite deposits at Pyrite Hill and Big Hill within its Thackaringa project. These deposits
have been a primary focus for BHCL and its predecessors since the mid 1970s.
The Thackaringa project comprises two small mining leases centred over the Pyrite Hill and Big Hill
cobaltiferous pyrite deposits. The Thackaringa cobaltiferous pyrite mineralisation is reportedly
stratiform and stratabound, occurring within a plagioclase-quartz-pyrite gneissic rock of the
Thackaringa Group. The Thackaringa Group rocks have been complexly deformed, with the Pyrite Hill
deposit interpreted to lie within the nose of an open, moderately east-plunging antiform whilst the Big
Hill deposit is located along the northern limb of a synform.
Currently reported Inferred Mineral Resources at Pyrite Hill and Big Hill include:
Inferred Mineral Resources
Project
Cut-off (lb/t Co)
Mt
lb/t (Co)
Pyrite Hill
1.1
10.6
2.2
Big Hill
1.1
4.4
2.0
In Snowden’s opinion the resource estimates and attributed confidence classifications for the Pyrite Hill
and Big Hill deposits, which have been reported in accordance with the JORC Code 2004, are
reasonable, given the available data.
On-going exploration and metallurgical assessment programmes at the Thackaringa project have
shown that most of the cobalt lies in solid solution with pyrite, requiring the application of specialised
metallurgical techniques to efficiently and economically extract the cobalt. Various metallurgical trials
have shown that the cobaltiferous pyrite can be readily concentrated and the cobalt contained in the
pyrite is recoverable by recognised processes. Opportunities have been identified for the application
of emerging technologies, and the recovery and sale of by-products and co-products including
feldspar, sulphuric acid, elemental sulphur, hematite and rutile.
Previous work has been limited to scoping, conceptual or valuation studies, with no formal,
comprehensive assessment completed at a pre-feasibility or feasibility study level. BHCL has
proposed a two year work programme designed to ascertain the feasibility of developing a viable
operation at Thackaringa focussed on the development of the Pyrite Hill resource. Evaluation of the
production potential at the Big Hill resource and any additional resources defined elsewhere on
BHCL’s near-by tenement areas would then be considered at a later stage.
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The Pine Ridge project area is considered by Snowden to be prospective for the discovery of
additional low-grade, Pyrite Hill-style cobaltiferous pyrite deposits as well as base metals, silver, gold
and possibly tungsten. Considerable areas of the Pine Ridge project are overlain by alluvial cover and
remain largely untested by modern exploration techniques.
The North East Extensions prospect includes the north-east extension of the mineralised host unit at
Big Hill. Mapping, sampling and drilling indicate the presence of pyrite-rich host rocks with similar
cobalt grades to those at Big Hill and Pyrite Hill.
The Himalaya North (Broken Hill-type) prospect lies at the north-eastern end of a 2 km long series of
base metal soil anomalies which extend north-east from the historic Himalaya polymetallic mine. The
Himalaya North prospect area hosts rock units which are also considered favourable for hosting small
gold deposits, given the discovery of gold in similar rocks at the proximal Pinnacles Mine and other
mines at Broken Hill, which lie outside BHCL’s current Pine Ridge project area. The Pyramid Hill
prospect is located 2 km north of the Pyrite Hill deposit and is a newly discovered area prospective for
Broken Hill-type copper-gold mineralisation.
In Snowden’s opinion the Broken Hill projects remain prospective for the discovery of additional lowgrade stratiform cobaltiferous pyrite deposits located along strike of the defined resources at Pyrite Hill
and Big Hill. In addition, the project tenements are considered prospective for gold, base metal, tin,
rare earth and possibly tungsten mineralisation. Snowden considers BHCL’s Broken Hill project areas
to be of merit and worthy of further exploration.
In order to progress its project areas, BHCL has proposed a two year evaluation and exploration
programme comprising:
•
pre-feasibility and feasibility studies of the Pyrite Hill cobaltiferous pyrite deposit, including
the validation of existing data, further drilling, establishing a feasible process path and
product markets, establishing Mineral Resource and Ore Reserve estimates, establishing
project capital and operating costs, preparing a mine plan and determining the economic
feasibility of the project; and
•
further exploration of the Broken Hill greenfields projects through compilation and validation
of existing exploration data, geological mapping, geochemical sampling plus focussed
geophysical data acquisition and interpretation, drilling and geological modelling.
BHCL has budgeted expenditure of A$3.62 M over its initial two year period to complete its proposed
work programme, which includes A$0.9 M in corporate overheads. A summary of the proposed
expenditure is presented in Table 1.1.
Table 1.1
Summary of BHCL’s work programme and budget (A$M)
Project
Year 1
$000
Year 2
$000
Total
$000
Pyrite Hill / Big Hill
670
1,700
2,370
North East Extensions
120
80
200
Himalaya Extended
14
60
70
Pine Ridge
25
54
80
Corporate costs and overheads
450
450
900
Total
1,280
2,340
3,620
In order to fund its future evaluation and exploration programmes it is BHCL’s intention to list on the
Australian Securities Exchange (“ASX”) by offering 25 M ordinary shares at an issue price of $0.20, to
raise a total of $5 M before the costs of the issue. There is also the facility for an over subscription of
up to 10 M shares to raise an additional $2 M.
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Snowden considers that the budgeted work programmes proposed by BHCL for the on-going
evaluation of its Broken Hill exploration projects have been well defined and are appropriate.
Furthermore, it is Snowden’s opinion that project evaluation studies to extract the cobalt mineralisation
conducted to date at the Thackaringa project have been preliminary in nature and do not provide a
realistic indication of the potential feasibility of developing a viable mining and processing operation at
Pyrite Hill.
Snowden contends that the production of a cobaltiferous pyrite concentrate for sale to a sulphuric acid
producer may provide the best opportunity for a successful project development.
In Snowden’s opinion the programme proposed by BHCL to progress the Thackaringa project has
been well defined and addresses the matters necessary to produce a Feasibility study upon its
completion. The expenditure budget is considered reasonable for the proposed programme, though it
may prove insufficient if an oxidation/hydrometallurgical process route is identified as the preferred
path during Year 1, requiring extensive additional test-work during Year 2.
2.
INTRODUCTION
BHCL is currently focused on the exploration and development of several mineral projects located in
the Broken Hill region of New South Wales, Australia. BHCL’s Broken Hill projects lie 20 km
southwest of the historic mining centre of Broken Hill in western New South Wales (Figure 2.1) and are
immediately adjacent the Transcontinental Railway.
BHCL is an unlisted public company which was incorporated in New Zealand in 1988 as the
Thackaringa Mining Company Ltd (“TMC”). At the time of its incorporation, BHCL was a fully owned
subsidiary of Southern Cobalt NL (“Southern Cobalt”) which subsequently changed it name to So Co
Ltd. In 1999, Heritage Gold (New Zealand) Ltd acquired a 33% interest in BHCL and has been sole
funding exploration and the assessment studies at the Thackaringa project since that time. BHCL is
currently 33% owned by Heritage and 67% owned by SoCo.
BHCL’s principal mineral assets in 1988 were the Thackaringa Mining Leases which host two large low
grade cobaltiferous pyrite deposits at Pyrite Hill and Big Hill. On-going exploration and assessment
programmes were conducted over these deposits during the 1990s through a number of joint ventures.
In addition, BHCL acquired further tenements throughout the 1990s, which were subsequently
consolidated into a single core property (EL6622) considered prospective for a variety of mineralisation
styles including lode-gold, Broken Hill type and metamorphosed volcanic hosted massive sulphide
(“VHMS”) base metal mineralisation. This exploration licence completely surrounds the Thackaringa
mining leases.
BHCL’s current mineral assets comprise a 100% interest in the Thackaringa and Pine Ridge projects.
The mining leases of the Thackaringa project are entirely surrounded by the Pine Ridge exploration
2
licences. The total tenement area is approximately 64 km .
Despite its proximity to Broken Hill, there has not been any mineral production of any significance from
BHCL’s Broken Hill tenements. However, studies completed by BHCL to date at its Thackaringa
project have outlined two low-grade cobaltiferous pyrite deposits at the Pyrite Hill and Big Hill
prospects.
The tenement status and BHCL’s equity in the Broken Hill projects is detailed in Table 3.1, and has not
been independently verified by Snowden. BHCL currently holds a 100% interest in the mining leases
(“ML”) ML86 and ML87 and in the exploration licence (“EL”) EL6622. Snowden is unaware of any
impediments relating to these leases.
BHCL intends to evaluate the cobalt deposits within the Thackaringa project by undertaking a prefeasibility study and if warranted, a Feasibility study. A primary focus of BHCL’s pre-feasibility study
will be the identification of appropriate processing steps which can be combined to create a practical
process route and enable a viable, economic project to be developed. BHCL’s Pine Ridge project is
also considered prospective for exploration targets of gold and base metal mineralisation. BHCL
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intends to undertake data validation prior to the commencement of field work to reassess the existing
targets or explore for other mineralised areas.
It is the intention of BHCL’s management to list the company on the ASX by offering 25 M ordinary
shares at an issue price of $0.20, in order to raise a total of $5 million before the costs of the issue.
There is also the facility of over subscription of up to 10 M shares to raise an additional $2 M. The
capital raised will be used to fund the future assessments of the projects discussed in this report.
Figure 2.1
3.
Location plan of BHCL’s Broken Hill projects (after BHCL)
GEOLOGICAL OVERVIEW
BHCL’s Broken Hill projects are centred on the southeastern corner of the Palaeoproterozoic
Curnamona Craton, which extends from the Broken Hill region in western New South Wales into
northeastern South Australia (Figure 3.1). The Curnamona Craton has undergone a prolonged history
of complex deformation, metamorphism and metasomatism, such that the original rocks are often
difficult to interpret. The majority of the Broken Hill district is composed of Willyama Supergroup highgrade regional metamorphic gneisses, schists and amphibolite, which have been subjected to at least
three phases of folding and intersected by large northeast and north-northwest trending shear zones.
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Table 3.1
Project
Tenement status for BHCL’s Curnamona Province projects
Tenement
Area
Held by
BHCL Equity
Thackaringa,
Pyrite Hill
ML86
205.9 ha
BHCL
100%
Thackaringa,
Big Hill
ML87
101.2 ha
BHCL
100%
Pine Ridge
EL6622
22 units
BHCL
100%
Notes
All exploration licences (ELs) are for Group 1 minerals (elemental minerals, metallic), mining
leases (MLs) are for cobalt, nickel, sulphur, iron, and iron-minerals.
A unit is the smallest unit of division of a New South Wales exploration licence. A unit has
dimensions of 1° longitude by 1° latitude, or approximately 300 ha
Figure 3.1
Curnamona Craton geological plan (after Primary Industries and Resources, South
Australia)
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The Curnamona Craton is best known as the host to the world-class Broken Hill lead-zinc-silver
deposit, which had a conservatively estimated 300 Mt of mineralised rock prior to mining. Current
research recognises the geological similarities of the Broken Hill district with other Proterozoic coppergold provinces throughout the world.
BHCL’s Broken Hill projects cover rocks of the Willyama Inlier, which in addition to hosting potential for
Broken Hill-type deposits are also prospective for a variety of other deposit types including silver, gold,
beryllium, cobalt, copper, lithium, nickel, lead, tin, tantalum, tungsten, zinc, platinum group elements
(“PGEs”) and uranium. The Pine Ridge project is considered by Snowden to be an early stage
exploration project whereas the Thackaringa project contains two identified cobaltiferous resources
(Pyrite Hill and Big Hill).
4.
THACKARINGA PROJECT
4.1
INTRODUCTION
BHCL’s 100% owned Thackaringa project comprises two mining leases, ML86 and ML87 (Table 3.1)
which are located some 20 km southwest of Broken Hill. These tenements cover a combined area of
307.1 hectares which overlie two large cobaltiferous pyrite deposits at the Pyrite Hill and Big Hill
prospects.
The geology of the project area is dominated by a thick sequence of amphibolitic and gneissic rocks
belonging to the Thackaringa Group which are partially buried beneath alluvial cover (Figure 4.1).
Figure 4.1
Thackaringa project geological plan (after BHCL)
The project has a history of exploration and investigation beginning in 1885 with the discovery of the
Big Hill sulphide mineralisation. Little then happened until 1951 when the Big Hill area was sampled
and mapped for lead and zinc. Cobalt was not reported until 1960 during a regional sampling
programme. Efforts since 1970 have focussed on delineating a cobalt resource and identifying a
practical processing route to extract the known cobalt mineralisation.
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4.2
PYRITE HILL
The Pyrite Hill deposit is hosted within a plagioclase-quartz-pyrite gneissic unit interpreted to form part
of the Himalaya Formation, which is located towards the top of the Thackaringa Group. The deposit
has been folded around the nose of the Camels Hump Antiform and extends for 800 m along the
northwestern limb and 400 m along the southern limb of this fold (Figure 4.2). The host unit generally
dips moderately to the east at about 50° (Figure 4.3) and consists of plagioclase, quartz and pyrite with
minor pyrrhotite, rutile and other metamorphically derived minerals. Mineralogical studies have failed
to identify any primary cobalt minerals, with almost all of the cobalt found to be in solid solution with
primary pyrite. A secondary coarse pyrite phase exists and was found to be depleted in cobalt.
Figure 4.2
Geological plan of the Pyrite Hill deposit (after BHCL)
A well developed gossan outcrops at surface surrounded by relatively fresh host pyritic rock. Previous
exploration has shown these rocks are oxidized to a depth of approximately 30 m and that cobalt may
be depleted in the oxidised zone. Drilling has found no evidence for secondary enrichment of cobalt.
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Previous diamond drilling indicates that the host rocks have been extensively deformed with
considerable thickening along the hinge of the anticline with attenuation of the fold limbs (Figure 4.4).
Pyrite-rich host rocks outcrop for about 1,500 m along the northwestern limb of the anticline. On the
southern fold limb, the thickness and pyrite content of the host unit decreases significantly. The
southern-most drillhole (80PYH13) intersected a potential cobalt mineralised unit higher in the
stratigraphic sequence.
Figure 4.3
4.3
Typical cross section through the Pyrite Hill deposit (refer to Figure 4.2 for location)
(after BHCL)
BIG HILL
The Big Hill deposit is located at the southwestern end of a series of gneissic outcrops that strike for
about 3,500 m and which also hosts the North East Extensions prospect to the northeast (Figure 4.1).
The line of outcrop forms the northern limb of the interpreted Big Hill Synform. The northern limb
generally dips to the north at about 65°. The plagioclase-quartz-pyrite unit appears to terminate
abruptly in the southwest in what is interpreted by BHCL to be a synformal fold closure (Figure 4.5).
The thickness of the host unit varies from about 60 m to 90 m and appears to be stratigraphically and
mineralogically equivalent to the Pyrite Hill host unit. As at Pyrite Hill, oxidation appears to have
resulted in depleted cobalt value with no evidence of secondary enrichment. The depth of oxidation is
reportedly highly variable.
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Figure 4.4
4.4
Illustrative long section through the Pyrite Hill deposit (refer to Figure 4.2 for location)
(after BHCL)
MINING AND EXPLORATION HISTORY
The Thackaringa project mining leases are entirely surrounded by the Pine Ridge project tenements
and hence the exploration and mining history of these two project areas is inextricably linked.
Snowden has therefore discussed the mining and exploration history of these two areas together.
The history of the Thackaringa and Pine Ridge project areas is summarised in Table 4.1. The project
tenements have been intermittently explored since the late-1880s by numerous companies and
extensive drilling of the Pyrite Hill and Big Hill deposits has been carried out since 1980 (Table 4.2).
Select results from this drilling are presented in the Appendix: Selected Drilling Results.
4.5
MINERAL RESOURCE ESTIMATES
A potential resource estimate was prepared for the Pyrite Hill project in 1981, prior to the advent of the
Australasian Code for Reporting of Exploration Results, Mineral Resources and Ore Reserves (JORC
Code, 1989). An approximate estimation of the resource at Big Hill was carried out in 1998. BHCL
has since reported these historic estimates as Inferred Mineral Resources. Snowden has reviewed the
Mineral Resource estimates with respect to the guidelines of the JORC Code 2004, and considers that
the Inferred Resource classification is appropriate. Whilst more sophisticated statistical methods exist
the estimation methodology and the resultant global resource estimates are appropriate considering
the available data. Snowden provides the following comments in relation to some specific aspects of
the resource estimates.
4.5.1
Data collection
Most of the drillhole data for the Pyrite Hill and Big Hill deposits were collected by only two of the
previous exploration companies and consisted of NQ sized diamond holes with percussion pre-collars
and RC percussion holes.
Drillhole locations at Pyrite Hill were set out using a previously established grid. This grid used
drillhole TH1 as its datum with an assumed elevation of 300 m. The grid was set out using a theodolite
and tape. No surveying of actual collar locations is documented. During Snowden’s previous
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inspection of the site many of the drill sites and some collars were sighted. However, many collars
appear to have been destroyed. While Snowden was unable to independently confirm the location of
some of the collars, sufficient drill sites were sighted to confirm the general location, distribution, and
amount of drilling. BHCL’s proposed exploration budget includes the compilation of an accurate
survey of the existing collars.
Figure 4.5
Geological plan of the Big Hill project (after BHCL)
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Table 4.1
Mining and exploration history at the Thackaringa and Pine Ridge projects
Period
1885 – 1889
Description
First exploration and mining in the area by Big Hill Silver Mining Company. The main focus was
the discovery of silver and lead. Three shafts were sunk and an adit developed into Big Hill.
Several shafts and pits on Pyrite Hill probably date from this period. Silver occurrences for Big Hill
may have been falsely reported.
1951
Sampling and mapping of the Big Hill mine workings occured in 1951, with samples reporting no
lead or zinc. The samples were not assayed for cobalt.
1960
The first cobalt was reported at Pyrite Hill and Big Hill during a regional sampling programme for
cobalt.
1965
Geological mapping, ground magnetics, and bedrock auger sampling over Pyrite Hill searching for
BHT lead-zinc deposits was carried out. No BHT mineralisation was found.
1967
The first diamond drillhole, TH1, to 998 ft (304 m) through the fold axis of the Pyrite Hill
plagioclase-quartz-pyrite rock was completed. This drillhole intersected 64.4 m of 2.43 lb/t cobalt
from 123.4 m down the hole. It had a true thickness calculated to be 62.21 m.
1968
An induced polarisation (“IP”) survey over Pyrite Hill was carried out reporting a strongly
anomalous zone over Pyrite Hill.
1970
Further IP surveys were conducted extending the anomalous zones at Pyrite Hill and Big Hill.
Further holes were drilled: TH2 (148.6 m); and TH3 (141.4 m) at Pyrite Hill; and BH1 (102.7 m);
and BH2 (104 m) at Big Hill.
All drillholes intersected significant cobalt mineralisation.
Mineralogical and metallurgical test-work found that cobalt occurred in solid solution with pyrite.
Traces of the cobalt bearing sulphide, bravoite (iron, nickel, cobalt) were also found.
1975 – 1977
The cobalt potential of the Thackaringa area was assessed as part of a larger regional programme.
This work included geological mapping and surface sampling. At the end of the evaluation it was
recommended that no further work be performed.
1976
Exploration commenced at the Himalaya Extended project.
1979
A costean was excavated near TH2 to obtain a bulk sample for metallurgical test-work.
1980
A dramatic rise in cobalt prices reignited interest in the Thackaringa area and a joint venture was
entered into. A further eight combined percussion and diamond drillholes to test for secondary
enrichment in the oxide zone at Pyrite Hill and Big Hill (drillholes 80PYH1 to 80PYH 04 and
80BGH5 to 80BGH8) was carried out. The drillholes failed to locate any secondary enrichment
material.
Concurrently, further exploration was carried out at the Himalaya Extended project.
1980 – 1981
The exploration strategy prior to completing further drilling and mapping at the Pyrite Hill project
was re-assessed. Diamond drillholes 80PYH5 to 80PYH14 were drilled. A potential resource
using a long-sectional polygonal technique was calculated and metallurgical test-work on a number
of drillhole samples was completed.
1984
Exploration for BHT mineralisation at Himalaya Extended was completed.
1988
TMC acquired the Thackaringa Project.
1993 – 1994
Under an option agreement with SoCo, MGM1 and MGM2 were drilled at Pyrite Hill for further
metallurgical test-work including flotation and bioleach testing.
1998
SoCo entered a joint venture agreement and undertook mapping and sampling at Pyrite Hill, Big
Hill, and the North East Extensions. TC98C03 to TC98C10 were drilled at Big Hill and a resource
using a cross-sectional polygonal method was calculated. Drillholes TC98C01, TC98C02, and
TC98C11 were drilled in the North East Extensions. A cross-sectional polygonal resource estimate
was completed on Pyrite Hill to confirm the previous estimation.
1999
SoCo’s partner withdrew from the joint venture agreement. Heritage acquired 33% of BHCL and
entered an agreement to investigate the Pine Ridge project. Heritage commissioned additional
metallurgical assessment work.
2002
Exploration of the Himalaya Extended area for copper-gold-cobalt mineralisation commenced.
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Drill core was sampled at two metre intervals and according to geological boundaries. Core was
reportedly split using impact methods with samples submitted for analysis for cobalt, sulphur and
nickel.
A drill rig mounted sample splitter was used to collect about three kilograms of RC chips over one
metre intervals in pyrite-rich zones, two metre intervals in pyrite-poor zones, and five metre intervals in
other zones. Mostly dry conditions for the RC drilling were reported.
No diamond drill core was available for Snowden to inspect. BHCL believes that drill core may be
stored in Broken Hill but was uncertain of its specific location at the time of writing. RC samples were
not systematically archived by the various exploration companies. Some RC samples are stored by
BHCL in Broken Hill but as the coarse fraction has been removed for metallurgical test-work, Snowden
did not consider that these samples were representative.
Table 4.2
Project
Pyrite Hill
Big Hill
North
East
Extensions
Summary of drilling at the Thackaringa and Pine Ridge projects
Year
1967
Drillholes
TH1
Types
Diamond
Total (m)
304
1970
TH2 and 3
Diamond
290
1980
80PYH1 – 4
Percussion with
diamond tail
166
1981
80PYH5 – 14
Percussion with
diamond tail
1,219
1993
MGM1 and 2
Percussion with
diamond tail
250
Sub-total
2,229
1970
BH1 and 2
Diamond
207
1980
80BGH5 – 8
Percussion with
diamond tail
226
1998
TC98C03 – 10
RC
858
Sub-total
1,291
RC
235
Sub-total
235
Total
3,755
1998
TC98C01, 2, and 11
An Eastman multishot camera was used for downhole surveys of the 1980 and 1981 drillholes at Pyrite
Hill. These surveys showed only minor deviation from design. A downhole survey of inclination only,
was carried out on a single RC hole at Big Hill (T98C10). This survey showed minimal deviation and
all unsurveyed holes were assumed to be true to design. Downhole survey data were not available for
Snowden to review.
Detailed geological logs were available for inspection by Snowden for most of the Pyrite Hill and Big
Hill drilling. Snowden is satisfied that the level of geological detail in these logs is sufficient for the
interpretation and modelling of the resource.
The drillhole logs of the holes completed in 1980 and 1981 contain detailed core recovery records
showing recovery of 100% for most intervals and only rarely, intervals with less than 90% recovery.
No data was available for recoveries from the other RC drilling programmes.
Snowden considers the data collection and survey methods used are sufficient for the classifications
adopted in BHCL’s resources estimates. Snowden recommends that the location of holes be
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confirmed, where possible, before upgrading the currently defined resources from their Inferred
classification.
4.5.2
Assay and sample QA/QC
Assay data was previously verified through manually checking assay results, re-assaying of selected
holes, and umpire check assaying of previous results using recognised analytical laboratories –
Analabs Limited (“Analabs”) and ALS Laboratory Group (“ALS”). Some errors were found and
corrected through this process. Snowden found no documented evidence for the use of standards,
blanks or field duplicates.
Figure 4.6 presents a scatter plot of umpire assay results and original results for Pyrite Hill. The
Analabs umpire assays demonstrate a significant bias that increases with grade. The ALS umpire
assays and the replicates of the original assays show a good correlation with the original results. On
this basis, it was concluded that the Analabs results were in error because of calibration issues.
Snowden considers that this conclusion is reasonable given that the ALS results and internal
laboratory replicates are in agreement with the original assay results. However, the issue of bias can
only be fully resolved after additional drilling and the collection of further QA/QC data.
Snowden considers that the assay quality is sufficient for the current resource estimates at Pyrite Hill
and Big Hill. Snowden recommends that a systematic and thorough QA/QC programme be
implemented for future drilling campaigns.
Figure 4.6
Scatter plot of check assays for Pyrite Hill
3,500
Analabs, Umpire
3,000
ALS, Umpire
ZincCorp, Replicate
Check Analysis (cobalt ppm)
2,500
2,000
1,500
1,000
500
0
0
500
1,000
1,500
2,000
2,500
3,000
3,500
ZincCorp Original (cobalt ppm)
4.5.3
Bulk density
A downhole geophysical density probe was used on the holes drilled in 1980 and 1981 to determine
bulk densities for resource tonnage estimation. The accuracy of the density probe determinations was
checked by measuring the density of 28 samples from six drillholes using the water immersion
technique. It was concluded that the downhole density probe results were sufficiently accurate for
resource estimation purposes. Figure 4.7 is a scatter plot of the density results for the 28 samples. It
shows that, with the exception of two outliers, the immersion method gives a slightly higher result than
the downhole probe.
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For the five drillholes not surveyed using the density probe, a regression relationship was used
between cobalt grade and density to assign density values. No evidence or data was available to
demonstrate this relationship between density and cobalt or sulphur grade.
3
For the mineralisation at the Big Hill deposit an assumed density of 2.8 t/m was used. This density
was derived from the Pyrite Hill data. Snowden considers this approach reasonable for the purposes
of producing the current Inferred Resource estimate at Big Hill.
Figure 4.7
Scatter plot of water immersion and downhole probe density determinations
Immersion and Downhole Probe
4.50
Probe Results (t/m 3)
4.00
3.50
3.00
2.50
2.00
2.00
2.50
3.00
3.50
4.00
4.50
Im mersion results (t/m 3)
4.5.4
Geological interpretation
Pyrite Hill
A 1.1 lb/t cobalt lower cut-off was used to define mineralised shapes within the plagioclase-quartzpyrite host rock in the polygonal long-sectional geological model. This approach assumed that
intersections were continuous between drillholes.
For some drillholes multiple mineralised
intersections have been interpreted. The thickness of the interpreted mineralised unit varies
considerably and Snowden considers that the polygonal long-sectional approach oversimplifies the
interpretation. Snowden recommends that future interpretations are based on cross-sectional and plan
projections of the mineralisation and that a three-dimensional model is constructed for the resource
estimation.
Outcrop at Pyrite Hill in the thicker fold axis zone indicates that the deposit is more structurally
complex than currently interpreted. Consequently Snowden considers that more detailed drilling and
mapping will be needed to allow this complexity to be incorporated into future models.
Big Hill
At Big Hill, a cross-sectional interpretation with a 1.1 lb/t cobalt lower cut-off was used to define
mineralised shapes. The mineralised shapes are less continuous than Pyrite Hill at this cut-off.
Continuity is poor on section (down dip) and between sections (along strike), which may partially
reflect the amount and extent of the available data. Consequently Snowden considers that there is a
higher technical risk associated with the interpretation of the Big Hill deposit.
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In Snowden’s opinion, the geological interpretation used to model both the Pyrite Hill and Big Hill
resources is appropriate given the quantity and distribution of available data, and the nature of the
resultant resource estimates made, being global and of the Inferred classification.
4.5.5
Resource estimation
Pyrite Hill
The current Pyrite Hill resource was estimated in 1981. A polygonal long-sectional approach was
taken. Consistently mineralised drillhole intersections of at least five metres true thickness and at least
1.1 lb/t cobalt were projected to an inclined long-section. Polygonal areas of influence were drawn
around each intersection. Tonnes for each polygon were calculated by multiplying the true thickness
of the intersection by the area of the polygon and the density as determined from downhole density
probe results or cobalt grade regressions. The unweighted mean grade of each intersection was
assigned to its respective polygon. The estimate was calculated for an area from the projected
outcrop of the ore zone to the 100 mRL. The resource was reported as above and below the
200 mRL.
In 1998, the Pyrite Hill resource was re-calculated using a cross-sectional polygonal method. A
1.1 lb/t cobalt cut-off was used to define mineralised shapes and the calculation was restricted to
above the 200 mRL and a 35 m depth of oxidation to restrict the up dip portion of the resource
estimation. The 1998 reported resource was also restricted by a simple pit shell with 50° walls.
The 1998 resource estimate is smaller and slightly higher in grade (Table 4.3) which probably reflects
of the use of a simple pit shell to further restrict the reported resource and differences in the applied
resource boundary locations. BHCL are using the 1981 estimate as their current measure of Inferred
Resources at Pyrite Hill.
Table 4.3
Comparison of the Pyrite Hill tonnes and grade estimates at a 1.1 lb/t cobalt cut-off
(above 200 mRL)
Estimate
Tonnes (Mt)
Grade (lb/t cobalt)
1981
10.6
2.2
1998
7.7
2.4
Big Hill
Resource estimates for Big Hill were first calculated in 1998 using a cross-sectional polygonal method.
A 1.1 lb/t cobalt cut-off was used to define mineralised shapes. The calculation was restricted to
100 m vertical depth and by a simple pit shell with 50° walls. BHCL’s current resource for Big Hill is
based on the 1998 estimate of 4.4 Mt at 2.0 lb/t cobalt (Inferred).
Snowden’s review of the resource estimates for Pyrite Hill and Big Hill indicate that the global tonnage
and grade estimates are reasonable and extreme high grades are not over-represented.
4.5.6
Resource classification
The resources at Pyrite Hill and Big Hill are classified as Inferred by BHCL. The Inferred classification
for Pyrite Hill applies only to the resource above the 200 mRL. Estimation of the Pyrite Hill resource
was performed before the advent of the JORC Code. Pyrite Hill’s initial classification was as “potential
resources”.
Snowden notes that in 1998, it was stated that the Big Hill resource “…has not been carried out with
rigour and is not quotable in releases”. The resource has since been classified as Inferred.
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Based on the checks performed by Snowden and others, Snowden considers that the Inferred
classification of both resources is appropriate, provided that only global resources are quoted and no
cut-offs or subdivisions are applied.
Snowden considers that the data at Pyrite Hill is sufficient to understand the continuity of geology and
mineralisation for a global resource. Data at Big Hill is also sufficient to deduce the continuity of
geology and mineralisation; however Snowden believes there is a higher risk associated the Big Hill
mineralisation, particularly for its continuity down dip.
Resource confidence can be improved at Pyrite Hill and Big Hill through further drilling. This improved
confidence may have the added benefit of allowing for selective mining studies to be undertaken.
4.6
MINING AND PROCESSING STUDIES
No relevant mining, hydrological or geotechnical studies have been completed over the Big Hill or
Pyrite Hill cobalt deposits in order to estimate an Ore Reserve in accordance with the guidelines of the
JORC Code 2004. However, the available information (primarily drill logs and studies completed to
date) suggests that:
•
unusual or difficult conditions are unlikely to be encountered by any future mining operation;
•
the mineralisation outcrops so a low mining strip ratio is likely to be achieved;
•
the low degree of weathering and high core recoveries recorded from drillholes suggest
relatively steep pit walls are achievable;
•
logging of core samples by previous explorers suggests blasting will be required for most of
the potential ore; and
•
the reporting of a low occurrence of water in drillholes suggests a low impact on mining from
ground water can be expected.
For clarity, the following definitions are adopted for the ensuing discussion on processing options for
the Thackaringa project:
•
concentration is the upgrading of the proportion of a valuable mineral, compound or element
in an ore stream by retaining the valuable material and rejecting material of lower or no
value.
•
oxidation is the chemical break-down of a mineral which contains a valuable element to allow
recovery of the valuable element.
•
leaching is dissolving the valuable element into solution.
•
purification is recovering the valuable element from a leach solution.
Metallurgical test-work to date on the Thackaringa deposits has included the following:
1970
•
flotation tests were conducted to produce a cobaltiferous pyrite concentrate.
1980
•
calcining test-work was conducted to produce a soluble cobalt sulphate by sulphatising
roasting; and
•
autoclave leaching of material from the deposits ground to -74µm was examined.
1994
•
BacTech Mining Corporation (“BacTech”) tested bacterial leaching in columns on drill chips
crushed to -15mm;
•
BacTech undertook flask leaching tests of cobaltiferous pyrite concentrate simulating
agitated tank leaching. This gave the highest cobalt extraction seen to date at 80-90% with a
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five day residence time. This was accompanied by separate flotation and comparative
grindability work on the material; and
•
various tests were conducted on extracting cobalt from synthetic liquors approximating the
composition of bacterial leach liquors.
1998
•
Amdel conducted gravity and magnetic separation test-work .
2000
•
BacTech conducted bacterial oxidation test-work on +6mm pieces of mineralised rock; and
•
EM Technologies performed small scale scoping tests using microwaves as a means of
oxidising the sulphides.
2004
•
Micron Research Pty Ltd undertook column and tray leaching of crushed drill chips simulating
heap leaching.
The previous test-work indicates that the Thackaringa sulphides can be readily concentrated and
roasted, and that leaching of the cobalt from the concentrate can be achieved. Economic whole-of-ore
hydrometallurgical oxidation or leaching is yet to be demonstrated.
4.7
DEVELOPMENT OPTIONS
BHCL has identified a number of development options for the Thackaringa project encompassing a
range of possible treatment routes for the recovery of cobalt.
The options identified by BHCL include:
•
on-site concentrate production followed by oxidation, leaching and purification;
•
on-site concentrate production followed by off-site concentrate oxidation, leaching and
purification by BHCL or others; and
•
on-site whole-of-ore heap leaching followed by purification.
The options identified for Thackaringa use recognised process steps. These steps have undergone
limited amenability testing with the Thackaringa cobalt mineralisation and encouraging results were
returned from this work. No work has been conducted to identify or optimise an efficient pit-to-product
process path.
Factors influencing the selection of the preferred process path include:
•
recovery efficiency at each process step;
•
process contaminant impact and management;
•
capital and operating costs;
•
waste stream generation and management;
•
production and marketing of by-products and co-products. Possible opportunities exist for
feldspar, mica, rutile, hematite, sulphuric acid and elemental sulphur;
•
commodity price forecasts and volatility; and
•
external factors including existing local and remote facilities and infrastructure. In particular,
relevant favourable factors include the proximity of Thackaringa to the city of Broken Hill
which has a population of approximately 20,000; the availability of power and potable water
supplies at Broken Hill; proximity to trans-continental road and rail networks; the presence of
substantial industrial works including the base metals smelting facilities of Nyrstar SA/NV
(“Nyrstar” formerly Zinifex Limited), at Port Pirie 350 km southwest of Thackaringa; and the
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on-going establishment of further industrial facilities at Broken Hill in support of the new
Murray Basin mineral sands mining activities.
4.8
REVIEW OF MINERALOGY AND PROCESSING ISSUES
4.8.1
Mineralogy
The mineralisation at Pyrite Hill and Big Hill reportedly consists of coarse to very coarse cobaltiferous
pyrite in a hard and structurally massive albitic quartzose gneiss. The hangingwall and footwall host
more ferro-magnesian silicate minerals (mainly biotite) and schistose non-pyritic gneisses. Pyrite
content varies from 10% to 90%, with a mean pyrite content of 15 to 20%.
Mineralogical analysis has shown the presence of primary and secondary pyrite. Secondary pyrite
displays very fine, porous colloform texture, whilst primary pyrite is developed as its characteristic
cubic habit. Cobalt is preferentially associated with the primary pyrite.
Work to date has shown that almost all of the cobalt is contained in solid solution within the iron
sulphide (pyrite) lattice with a mean content of 0.5% cobalt. Cobaltiferous pyrite typically has an iron to
cobalt ratio of 100/1. There is negligible cobalt in the ferro-magnesian silicates (ie biotite).
Destruction of the pyrite matrix is required in order to release the cobalt for recovery by subsequent
leaching.
4.8.2
Concentration
Test-work shows that a high grade pyrite concentrate containing cobalt can be produced with a cobalt
recovery above 90% using the sulphide flotation method. Mineralogical work completed by Amdel in
1970 suggested that the pyrite was substantially liberated at a very coarse size (around 300 microns)
implying a low grinding cost prior to flotation. This mineral characteristic also suggests gravity
concentration may be an alternative to flotation.
Further concentration of the cobalt content may be possible using a combination of hydrometallurgy
and flotation. The secondary pyrite is more amenable to attack by leaching agents than the primary
euhedral pyrite. This characteristic could be exploited to alter the secondary pyrite to enable it to be
rejected in a flotation stage, upgrading the cobalt content of the retained fraction.
The mineralisation also contains a quantity of the magnetic iron sulphide mineral, pyrrhotite, which
contains low levels of cobalt. A magnetic separation step could be used to separate the pyrrhotite
from the non-magnetic portion of a sulphide concentrate, thus providing further upgrading of the cobalt.
The production of a cobaltiferous pyrite concentrate is a relatively low risk, low capital cost and low
operating cost process. The concentrate is likely to be suitable for further processing by a leaching
process to recover the cobalt, or for direct sale to a sulphuric acid producer.
The production of a cobaltiferous pyrite concentrate should not compromise the potential for the
project to produce industrial minerals such as mica, ceramic grade feldspar and glass grade feldspar,
which could be recovered from the tailings produced during the concentration stage.
Potential markets for the sale of cobaltiferous pyrite concentrate include commercial and industrial
sulphuric acid plants which use pyrite concentrate as feedstock for roasting. With some plant
additions, cobalt and other by-products may be recoverable from the cinders produced. Snowden
notes that there is currently no significant market for sulphuric acid nor pyrite concentrate for acid
production in the Broken Hill region. With continuing exploration in the area, there is the possibility that
this may change if future mineral projects utilising leach technology come into production in the region.
There is however a potential future sulphuric acid deficit in South Australia as it is used as the lixiviant
(ie the liquid media designed to selectively extract the desired metal from the ore) for uranium
production at BHP Billiton Limited’s Olympic Dam operation. The Olympic Dam operation currently
produces its own sulphuric acid from its copper smelter off-gases, burning imported brimstone
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(elemental sulphur) and trucking in acid from Nyrstar’s smelter at Port Pirie. Snowden understands
that BHP Billiton’s proposed expansion plan at Olympic Dam will require more acid than what would be
available as by-product from copper smelting. In addition to the potential market at Olympic Dam,
BHP Billiton’s Ravensthorpe nickel-cobalt plant in Western Australia also has an on-site brimstone
burning sulphuric acid plant.
Both Olympic Dam and Ravensthorpe may present potential market opportunities for BHCL’s
cobaltiferous pyrite concentrate. Ravensthorpe may however provide a better opportunity as cobalt
recovery on site may also be possible.
4.8.3
Pyrite Oxidation
Test-work has been conducted on the Thackaringa mineralisation which shows that the pyrite can be
oxidised by pyrometallurgical and hydrometallurgical (including heap leaching) methods.
Pyrometallurgy
The pyrometallurgical approach to oxidation (roasting) treats the cobaltiferous pyrite concentrate by
using high temperatures and oxygen to drive off the sulphur and break down the pyrite matrix, leaving
cobalt in the cinders for subsequent leaching. During the process, the sulphur can be collected and
used to manufacture sulphuric acid potentially providing BHCL with an additional income stream.
Hydrometallurgy
Hydrometallurgical oxidation methods can be applied to the complete ore stream or to a previously
prepared concentrate.
Hydrometallurgical oxidation of cobaltiferous pyrite concentrates can be achieved by pressure leaching
(elevated pressure and temperature in an acid environment) or bio-leaching (acidic solution inoculated
with an appropriate bacterial agent) methods, leaving the cobalt exposed for leaching. Leaching of the
cobalt occurs during the same process step.
The whole-of-ore heap leach method of oxidation involves construction of large heaps of ore which are
irrigated with an acidic solution inoculated with a bacterial agent appropriate for breaking down the
pyrite. Leaching of the cobalt occurs during the same process step.
Processing a whole-of-ore feed through a processing plant (rather than in heaps) is not considered
practical as a much larger plant is required at what is likely to be a prohibitive capital cost. At the 5:1
concentration ratio for the pyrite (as suggested as being achievable by test-work), 1.0 Mtpa of ore
reduces to 0.2 Mtpa of pyrite concentrate for further processing, requiring a much smaller plant.
4.8.4
Leaching
Roasting
The roasting method of oxidation leaves cobalt in the cinders for subsequent leaching. Leaching the
cinders yields cobalt in solution for subsequent extraction and purification. Depending on the
completeness of the oxidation process, the cobalt may be left in a water soluble sulphate form or other
less reactive forms requiring acid leaching.
Hydrometallurgical oxidation
The hydrometallurgical oxidation processes are integrated with leaching and so may be categorised as
whole-of-ore, bio-leaching or pressure leaching. All result in a cobalt solution for subsequent
purification.
Heap leaching
Economic whole-of-ore leaching in heaps has yet to be demonstrated as being achievable with the
currently defined Thackaringa mineralisation. Previous test-work has returned poor results, with very
low cobalt extractions in column tests after 211 days of leaching. The poor results are due to the
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precipitation of jarosite resulting in co-precipitation of cobalt. This problem may be manageable. Heap
leaching requires large areas to be occupied by the heaps and has a long lead time to production.
Although heap leaching incurs a lower capital and operating cost compared to other leaching
techniques, purification costs are higher and product recoveries are usually lower.
Bio-leaching
Bio-leaching or pressure leaching of a pyrite concentrate should be interchangeable technologies for
the Thackaringa material. Both processes break down the pyrite and allow subsequent extraction of
the cobalt. Pressure leaching operates at elevated temperatures requiring oxygen injection but is a
high intensity process with a small “footprint” and is capital intensive. Bio-leaching in agitated tanks
does not use pure oxygen but requires large volumes of air delivered to the leach tanks and efficient
slurry mixing for sulphur oxidation. Power demand in bio-leaching can be high because the slurry has
to be cooled to remove the heat released from the exothermic reactions to protect the bacteria.
As for oxidation, leaching a concentrate would require a substantially smaller plant than that which
would be required if a whole-of-ore plant leach was conducted.
Emerging technologies such as microwave pre-treatment and the GEOCOAT leaching process have
been suggested as potentially being applicable though only the later has been in commercial use
treating refractory gold ore.
The GEOCOAT process is comparatively new bio-oxidation process which has been employed at
Ridge Mining Limited’s Agnes gold mine in South Africa. The process is designed to coat a sulphide
flotation concentrate onto crushed and sized inert carrier rocks. The coated rocks are stacked on an
impervious pad for bio-oxidation of the sulphides. The process typically uses mesophilic (ie bacteria
that are active at temperatures ranging from approximately 15 to 40°C) bacteria and is applicable to
the processing of refractory gold sulphide concentrates and the bioleaching of copper, nickel, cobalt
and zinc concentrates. GEOCOAT has not been tested on the Thackaringa material but may provide
an alternative bio-leaching option. Further test-work is required.
Snowden notes that all on site leaching options generate a large volume of low tenor acid effluent
which needs to be neutralised at additional cost, thereby negating the possibility of metallurgical
credits for the sulphur content. Neutralising acid effluent from the leaching options considered for
Thackaringa has received minimal attention in previous studies but in general one unit of sulphur will
produce three units of sulphuric acid requiring three units of lime for neutralisation. There may be
adequate limestone resources in the Broken Hill district for neutralisation, some of which were
th
developed to support the extensive lead smelting operations which operated in the late 19 century.
4.8.5
Purification
The product of leaching, the pregnant leach liquor, can be purified by chemical means, where an
insoluble compound is precipitated through chemical means, or by electro-winning where electrolysis
is used to plate pure metal onto an electrode. Electro-winning usually requires a preliminary solvent
extraction step to purify the leach liquor prior to electro-winning.
BHCL should consider producing a cobalt intermediate product by precipitating cobalt hydroxide or
cobalt sulphide from the pregnant leach liquor. While cobalt sulphide precipitate contains less
impurities than cobalt hydroxide there are severe occupational health and hygiene risks associated
with the use of hydrogen sulphide, which is required. Cobalt hydroxide is produced more simply by
increasing the pH of pregnant leach liquor through adding lime.
Producing a saleable cobalt intermediate product by precipitation rather than cobalt metal by electrowinning would appear to forgo sales revenue from the higher value product. However, the practical
reality is that commercial cobalt electro-winning plants are capital intensive, very difficult to operate
and require superb solution impurity control. Metal production through electro-winning could be
examined after the project is established and has been operating successfully for several years.
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4.8.6
Comparable operations
In assessing the potential viability of a new project, a comparison with similar operations should be
made. The only operation known to Snowden recovering cobalt from material similar to that at
Thackaringa is Kasese Cobalt (Kasese) in Uganda. At Kasese, cobaltiferous pyrite tailings are
bioleached in agitated tanks with the cobalt metal recovered by solvent extraction and electro-winning.
Kasese commenced operations in 1998. Its financial success was compromised early in its life by a
large capital cost over-run predominantly caused by construction difficulties ascribed to the location,
equipment failures and technical problems during commissioning, followed by on-going low cobalt
prices. Ownership passed from Banff Resources to Normandy Mining Ltd then to Newmont Mining
Corporation (Newmont). The operation shut down in 2002 but recommenced in early 2004 taking
advantage of higher cobalt prices after new owners, MFC Bancorp, purchased the property from
Newmont.
Any hydrometallurgical proposal for Thackaringa which deviates from the Kasese model must be
examined cautiously because it would require the development or adoption of new technology or a
process path not yet proven in a similar application. In general, there is a poor industry history of
transferring new hydrometallurgical technologies into successful production operations.
Comparing Kasese to the Thackaringa project leads to considering the difference in characteristics of
the two feed streams to whatever process is proposed to break-down the pyrite and expose the cobalt
for dissolution (leaching or roasting). The feed grade at Kasese is 1.3% to 1.5% cobalt while the
Thackaringa material will assay around 0.6% to 0.7% cobalt after producing a pyrite concentrate by
flotation. The Thackaringa pyrite concentrate will require the break-down of approximately twice as
much pyrite as Kasese to produce a unit mass of cobalt, requiring higher capital and operating
expenses. In addition, twice as much acid sulphate ion is produced which has to be managed through
neutralisation or put to an alternative use such as the production of sulphuric acid.
Some improvement in leaching performance over that achieved at Kasese might be possible if the
Thackaringa plant can use more thermophilic bacteria which survive at elevated temperatures (of up to
°
70 C).
4.8.7
Conclusion
BHCL consider an operation focused on producing a cobaltiferous pyrite concentrate for sale with
industrial mineral by-products has a low technical risk combined with the likely low capital and
operating costs, when compared to a hydrometallurgical process route producing an intermediate or
final cobalt product. This option would provide BHCL with time to pursue additional processing
technologies capable of retaining more of the value of the cobalt for its own account.
Snowden consider that the Thackaringa project has the following major advantages and
disadvantages, each representing opportunities or risks to achieving a positive feasibility study
outcome:
Advantages:
•
large volume resource;
•
low mining costs and risk;
•
high current cobalt spot price;
•
low deleterious element content;
•
favourable concentration characteristics;
•
potential value-adding by-products and co-products; and
•
proximity to infrastructure, facilities and transport.
Disadvantages:
•
low cobalt grade;
•
concentration (or upgrading) of cobalt grade limited by the inherent cobalt content of the
pyrite;
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•
technically difficult extraction of cobalt;
•
high cost extraction of cobalt; and
•
volatile cobalt market.
Snowden consider that for the Thackaringa project to be economically viable, BHCL will need to
receive credits for acid production in addition to its revenue from cobalt. If there is no market for the
acid production, this acid will need to be neutralised thereby adding additional cost to the project. This
additional cost may make the project a marginal proposition.
4.9
EXPLORATION POTENTIAL
In Snowden’s opinion, potential exists for further extensions to the currently defined cobalt resources
at Pyrite Hill and Big Hill, particularly at the North East Extensions prospect lying northeast along strike
from Big Hill, in the adjacent Pine Ridge Project, and also within the folded equivalents of the Pyrite Hill
plagioclase-quartz-pyrite rock which have been mapped in various locations within the current project
tenements. Many authors have documented a correlation between cobalt grade and pyrite content in
mineralised rocks. Future exploration should aim to delineate the location of favourable pyrite-rich
rocks and zones of high pyrite content. IP surveys carried out by previous explorers were successful
in further defining the pyrite-rich units at Pyrite Hill. This geophysical technique may be successful in
locating the position of favourable pyrite-rich rocks within the plagioclase-quartz-pyrite rocks mapped
in other areas of the project.
4.10
PROPOSED PROGRAMME AND EXPENDITURE
BHCL has prepared a work programme and budget for on-going assessment of the Thackaringa
tenements. A summarised version of the work programme and budget is presented in Table 4.4.
The Thackaringa project work programme budget comprises:
•
drilling, which provides for compiling and validating existing data and a drilling programme of
6,000 m of RC and diamond core holes for resource definition, metallurgical test-work and
engineering purposes;
•
pre-feasibility and feasibility studies including:
- metallurgy: which provides for concentration, oxidation, leaching and purification test-work
and a pre-feasibility options study in Year 1. Year 2 is for definitive test-work to establish a
process path for assessment in the feasibility study; and
- engineering: which provides for mine engineering and marketing studies at pre-feasibility
and feasibility study levels.
Table 4.4
Thackaringa project work programme budget
(A$M)
Activity
Year 1
$000
Year 2
$000
Total
$000
Infill drilling
300
500
800
Pre-feasibility and
Feasibility studies
300
1,100
1,400
Site management
70
100
170
Total
670
1,700
2,370
In addition to the costs shown in Table 4.4, corporate costs of A$0.9 M are anticipated over the two
year programme period, which includes costs attributable to gaining admission to the ASX.
Snowden considers that the Thackaringa programme has been well defined and addresses the
matters necessary to complete a Feasibility Study. The proposed budget is considered reasonable,
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though it may prove insufficient should an oxidation/hydrometallurgical process route be identified as
the preferred processing path during Year 1, in which case, extensive additional test-work will be
required in Year 2.
5.
PINE RIDGE PROJECT
5.1
INTRODUCTION
BHCL’s Pine Ridge tenements overlie portions of the Broken Hill and Thackaringa Group rocks, which
host the Broken Hill lead-zinc-silver deposit and other significant base metal deposits of the Broken Hill
region. Significant but mostly shallow (<5 m) alluvial cover is present throughout the Pine Ridge
project tenements.
BHCL currently holds a 100% interest in the Pine Ridge project which comprises a single exploration
2
licence (EL6622) with an area of some 64 km . The Pine Ridge project area completely surrounds the
Thackaringa project tenements.
Extensive geological mapping and rockchip sampling of EL6622 was completed by Mr W. Leyh of
Eaglehawk Geological Consulting Pty Ltd (“Eaglehawk”) in April and May of 2007. This work
highlighted a number of additional exploration targets (Figure 5.1) with the rockchip samples
confirming the style and grade of previously encountered mineralisation. Snowden considers these
targets are prospective for base metals, silver and gold and warrant further exploration follow up. The
most significant of these targets as defined by Eaglehawk are detailed below.
Figure 5.1
5.1.1
Location plan of exploration targets at the Pine Ridge project
North East Extensions
The North East Extensions prospect represents the northeastern continuation of the plagioclasequartz-pyrite unit which hosts cobaltiferous pyrite mineralisation at Big Hill. These host rocks are
mapped in outcrop for some 3,500 m along strike of Big Hill (Figure 5.2). Mapping, sampling and
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drilling completed to date indicate the presence of pyrite-rich host rocks in the North East Extensions
tenement with similar cobalt grades to those at Big Hill and Pyrite Hill.
Figure 5.2
5.1.2
Geological plan of the North East Extensions prospect (after BHCL)
Himalaya North
The Himalaya North prospect is located to the east of the Big Hill deposit within the southeastern
corner of EL6622 (Figure 5.1) and overlies rocks of the Broken Hill Group. Pasminco Exploration Pty
Ltd discovered a series of base metal anomalies extending over a 2 km strike length to the southwest
of the historic Himalaya mine. This system also extends 1.5 km to the northeast of the Himalaya mine
and into BHCL’s Pine Ridge project. The development of garnet quartzite and garnet sandstone within
this anomalous base metal zone is considered by BHCL’s consultant, G.W. McConachy and Co., to
indicate prospectivity for base metal and gold mineralisation.
Follow-up work involving geochemical rockchip sampling and detailed 1:1,000 scale geological
prospect mapping by Eaglehawk has confirmed the geological setting and prospectivity of the
Himalaya North prospect. The work has also highlighted the exploration potential for Broken Hill-type
mineralisation at the Himalaya North prospect and elsewhere on the Pine Ridge project.
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5.1.3
Pyramid Hill
The Pyramid Hill prospect is associated with shallow circa-1900s workings and is considered a Broken
Hill stratiform to stratabound base metal analogue (copper-gold). Lodes up to 10 m thick exist along a
strike length of greater than 500 m with potential for a further 200 m under cover. The prospect is
hosted by altered psammite, pelite and amphibolite (probably of the Broken Hill Group) as well as the
Potosi Gneiss and is prospective for copper and gold. From geological mapping the mineralisation
occurs in extensive, complexly folded, massive sulphide derived lodes.
5.1.4
Tower Hill
The Tower Hill prospect is considered a Broken Hill stratiform analogue. The prospect is hosted within
the lower to middle Broken Hill Group consisting of altered meta-sediments and amphibolite and the
Potosi Gneiss. The project contains extensive refolded zones greater than 40 m thick, a strike length
of 3 km and with lodes up to 4 m thick. Tower Hill is considered prospective for base metals,
principally lead, silver, zinc and possibly tungsten.
5.1.5
Ram Paddock
The Ram Paddock area includes repeated lode zones up to 20 m wide in a poorly exposed valley
area. The strike length is approximately 4 km long and there is evidence of minor historic open pits in
the area. Ram Paddock is considered prospective for cobalt.
5.1.6
Other areas
Other prospective areas highlighted by the Eaglehawk programme of geological mapping and rock
chip sampling include Alders Tank, the Old Coolgardie Tank, TSQV prospects, Pyrite Hill North and
the Camel Hump Area (Figure 5.1).
These areas warrant further exploration but are considered to be a lower exploration priority due to a
lesser degree of veining as well as increased soil cover.
5.2
EXPLORATION POTENTIAL
The anomalous zone extending to the northeast from the Big Hill pyrite deposit to the North East
Extensions prospect is considered by Snowden to be highly prospective for further cobalt
mineralisation. In addition, potential exists for additional cobalt mineralisation in the folded equivalents
of the Pyrite Hill plagioclase-quartz-pyrite rocks which have been mapped within the tenement.
Potential for base metal and gold mineralisation at the targets highlighted by Eaglehawk is supported
by the presence of similar rocks to those which have been found to contain gold and base metal
mineralisation at the nearby Pinnacles Mine and in other mines at Broken Hill.
Snowden notes that a significant portion of the Pine Ridge project area remains largely untested due to
the presence of extensive soil cover. Only one diamond drillhole has been drilled outside of the known
cobalt deposits with the historical exploration emphasis being on cobalt.
5.3
PROPOSED WORK PROGRAMME AND BUDGET
BHCL has prepared a work programme and budget for the on-going assessment of the Pine Ridge
project area. A summarised version of the work programme and budget is presented in Table 5.1.
As a precursor to further exploration, BHCL plans to digitally compile and validate all available data
and confirm the location of all previous drillholes. Given the uncertainty associated with some of the
data, particularly the exact location of drillholes, Snowden considers this approach to be appropriate.
IP geophysical surveying will be used across the North East Extensions project and followed-up with a
small number of targeted drillholes. The aim of this programme is to establish the continuity of the
pyrite-rich units and to find areas of elevated pyrite content and thus elevated cobalt grades. Given
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FINAL
the correlation between pyrite and cobalt grades and the demonstrated effectiveness of IP to define
the pyritic unit, Snowden considers this approach to be appropriate.
At the Himalaya Extended prospect, BHCL has proposed a programme of data compilation, mapping
and interpretation to identify new targets for drilling.
Table 5.1
Pine Ridge project work programme and budget (A$M)
Activity
Year 1
$000
Year 2
$000
Total
$000
Exploration
60
0
60
Drilling
60
140
200
Site management
40
50
90
Total
160
190
350
DECLARATIONS BY SNOWDEN MINING INDUSTRY CONSULTANTS
INDEPENDENCE
Snowden Mining Industry Consultants Pty Ltd is an independent firm of consultants providing a
comprehensive range of specialist technical and financial services to the mining industry in Australia
and overseas, through offices in Perth, Brisbane, Johannesburg, Cape Town, Vancouver, London and
Belo Horizonte. Our services include technical audits, project reviews, valuations, independent expert
reports, project management plans and corporate advice.
This report has been prepared independently and in accordance with the VALMIN and JORC Codes of
the Australasian Institute of Mining and Metallurgy (“AusIMM”).
The authors do not hold any interest in BHCL, its associated parties, or in any of the mineral properties
which are the subject of this report. Fees for the preparation of this report are being charged at
Snowden’s standard rates, whilst expenses are being reimbursed at cost. Payment of fees and
expenses is in no way contingent upon the conclusions drawn in this report.
QUALIFICATIONS
The principal personnel responsible for the preparation and review of this report were Mr Jason Froud
(Senior Consultant – Corporate Services), Mr Peter Myers (Principal Consultant Engineer), Mr Michael
Tyndall (Principal Consultant – Corporate Services) and Mr Peter Munro (Associate Principal
Consultant Engineer).
Mr Jason Froud (BSc (Hons), Grad Dip (Fin Mkts), MAusIMM) is a geologist with more than 11 years
experience in the mining industry. Jason has worked in mining geology and exploration roles in
Australian gold and copper deposits gaining skills in grade control, reconciliation, resource definition,
financial analysis and quality assurance and quality control. Since Joining Snowden, He has been
involved in independent technical reviews, audits and valuations of mining and exploration assets
covering a wide range of commodities.
Mr Michael Tyndall (BSc (Hons), Grad Dip (Min Eng), MAusIMM) is a geologist with a combined 10
years experience in marine and terrestrial diamond exploration and mining and a further five years
experience in mineral resource management on deep level gold mines in southern Africa. Key
expertise was gained in mineral project feasibility and technical due diligence studies. Over the past
two and a half years Michael has worked as a mineral industry advisor where he assisted in the
compiling and writing of independent techno-economic valuation reports for various commodity and
mineral asset types, mainly for the purposes of stock exchange listings and project capital funding. In
January 2009, Michael joined Snowden’s corporate division in Australia as a principal consultant.
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Mr Peter Myers, B Eng (Mining) (Hons), MAusIMM, is a mining engineer with 25 years experience in
underground, open pit and dredge mining operations. He has held senior operational and technical
roles including those with Departmental and Site Management responsibility. He has managed or
participated in a number of feasibility studies, major site capital projects, business improvement
projects, short, long term and life of mine plans, and mining development and production contracts.
Peter’s experience covers copper, nickel, zinc, lead and mineral sands operations employing
underground selective and bulk methods, hard rock open pit methods, and dry and dredge alluvial
methods. As a consultant, he has been involved in technical reviews, audits and valuations of
diamond, copper, nickel and gold open cut and underground mining projects.
Peter Munro, BAppSc, BEc, BCom, AAusIMM, is a Senior Principal Consulting Engineer with
Mineralurgy Pty Ltd, a Brisbane based specialist metallurgical consultancy. Peter gained extensive
experience in virtually all aspects of mineral processing and extractive metallurgy with a primary focus
on zinc, lead, silver, copper and gold during his 30 years with M.I.M. He has constructed,
commissioned and operated a variety of minerals processing plants, conducted technical reviews,
audits, efficiency enhancement projects and carried out due diligence evaluations throughout the MIM
group. His work in Mineralurgy Pty. Ltd. has included technical reviews, audits, due diligence
evaluations for initial public offerings and acting as banker’s engineer. Peter is a past member of the
Board of the Julius Kruttschnitt Mineral Research Centre and Adjunct Professor at the Department of
Mining, Metallurgy and Materials and at the Julius Kruttschnitt Mineral Research Centre, University of
Queensland.
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BIBLIOGRAPHY
Amdel Limited, 1998, “Separation and Analysis of Pyrrhotite and Pyrite.”
Arandis Pty Ltd, 1988, “Untitled note to Sirocco Resources NL.”
Ashland, M., 1976 “Interim Report on Big Hill/Pyrite Hill Pyrite Cobalt Deposit for Central Austin Pty
Ltd.”
Australian Anglo American Ltd., 1982, “Final Report to Jones Mining NL, Exploration Licence 1621,
Ophara Tank.”
BacTech, 1997, “Various reports to Southern Cobalt NL.”
BacTech, 2000, “High Temperature Bacterial Leaching Sighter Test on Thackaringa Cobalt Ore.”
Broken Hill Cobalt Ltd, 2005, “Focussed on a Cobalt Development and Gold and Base metal
Exploration in Central and Western New South Wales.”
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Castle, M.J., 1988, “The Pyrite Hill and Big Hill Cobaltiferous Pyrite Deposits.”
Clema, J.M., 1991, “Big Hill – Pyrite Hill, Cobalt-Sulphur-Iron Resource, Thackaringa, NSW.”
CRAE, 1977, “Report on Pyrite Hill/Big Hill Cobaltiferous Pyrite Deposits Broken Hill.”
CRAE, 1981, “Resource Potential Pyrite Hill, ML 86, Broken Hill District, NSW.” CRAE report number
10388.
CRAE, 1981b, “Results of Exploration, ML 87, Big Hill, Broken Hill District, NSW.”
number 10389.
CRAE report
CRAE, 1983, “Report to Accompany Application for Suspension of Labour/Expenditure in respect of
Mining Lease Nos. 86 and 87.”
CRAE, 1998, “Results of Diamond Drilling Programme to test for a secondary enrichment zone Big
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Department of Mineral Resources, NSW, 1959, “Review of Pyrite Deposit near Thackaringa.”
Devlure Pty Ltd, 2004, “Independent Process Review.”
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Broken Hill, NSW.”
Eaglehawk Geological Consulting Pty Ltd, 2007, “Brief Summary on Geochemical Sampling and
Geological Mapping – EL6622 Pine Ridge Project, Thackaringa Area, Broken Hill NSW.”
Eaglehawk Geological Consulting Pty Ltd, 2007, “Report on detail geological mapping Pyramid Hill and
Himalaya North prospects and the wider exploration potential of EL6622, Pine Ridge project,
Thackaringa area, Broken Hill, NSW.”
Eaglehawk Geological Consulting Pty Ltd, Undated, “Pinnacles Mining Leases.”
Elephant Mines Pty Ltd., 2004, “First Annual Report, EL6045 Euriowie.”
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EM Technologies Inc, 2000, “Scoping Test Results for Heritage Gold.”
Farrell and Associates, 1987, “The Potential of the Big Hill-Pyrite Hill Prospect, Broken Hill District,
NSW, as a Sulphur-Cobalt Resource.”
G. W. McConachy and Co, 2004, “Independent Geologist’s Report on Mineral Properties.”
Geo. Surv. of NSW, 1908, “The Copper Mining Industry and the Distribution of Copper Ores in New
South Wales.”
Geo. Surv. of NSW, 1980, “Geology of the Thackaringa 1:250,000 Sheet, Broken Hill.” Report GS
1981/039.
Geo. Surv. of NSW, 1982, “Non-metallic and Tin Deposits of the Broken Hill District.” Bulletin 28.
Geo. Surv. of NSW, 1996, “Geology of New South Wales – Synthesis.”
Framework. Memoir Geology 13 (1).
Volume 1, Structural
Geo. Surv. of NSW, 1997, “Geological Digital Data package for the Goulburn 1:250,000 Sheet, Version
1.” (Published on CD-ROM).
Geo. Surv. of NSW, 1997, “Metmin 97 Data package” NSW Metallic Mineral Occurrence database
and Accompanying ArcView/MapInfo Coverage.
Geo. Surv. of NSW, 2002, “Potential for Sediment Hosted lead-zinc in the Paragon Group, Broken Hill
Region, New South Wales.” Report GS 2002/236.
Geo. Surv. of NSW, 2003, “Gold Prospectivity in the Broken Hill Block, New South Wales, Project
Progress to July 2003.” Report GS 2003/265.
Gilfillan Associates Pty Ltd, 1992, “Interim Report on Pyrite Hill and Big Hill, Thackaringa Hills, NSW.”
Glen, R.A., 1992, “Thrust, Extensional, and Strike-Slip Tectonics in an Evolving Palaeozoic Orogen – a
Structural Synthesis of the Lachlan Orogen of South-eastern Australia.” Technophysics, v. 214, p. 341
– 380.
Heritage Gold NZ Ltd, 2004, “Annual Report 2004.”
Hunter Exploration NL, 1998, “Report on Exploration Activities, May to June, 1998, Big Hill Prospect
and Extensions, ML 86 and EL 4521.”
Hunter Exploration NL, 1998, “Report on Exploration Activities, September to November, 1998, Big Hill
Prospect and Extensions, ML 86 and EL 4521.”
Jones Mining Ltd., 1985, “Exploration Licence 1621, NSW, Ophara Tank Project, Final Report.”
KH Morgan and Associates, 1996, “Evaluation of the Thackaringa Project for Southern Cobalt NL.”
Kvaerner Davey, 1997, “Thackaringa Cobalt Project – Review of Capital Cost Estimate.”
Kvaerner Davy, 1997, “Southern Cobalt NL Process Review.”
Kvaerner Metals, 1998, “Southern Cobalt NL Process Review.”
Macedon Gold Mines B.V., 1993-95, “Broken Hill Cobalt progress reports.” Various
Macedon Gold Mines B.V, 1994, “Bacterial Oxidation of Cobalt Ore.”
Macedon Gold Mines B.V, 1994, “Cobalt Bio-Leach Project.”
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Macedon Gold Mines B.V, 1994, “Thackaringa Cobalt Project Third Preliminary Feasibility Study.”
Macedon Gold Mines B.V, 1995, “Bacterial Oxidation of Cobaltiferrous Pyrite Concentrate.”
Macedon Gold Mines B.V, 1995, “Thackaringa Cobalt Project Status of Bacterial Leaching Work.”
Micron, 2004, “Bacterial Leaching Trials of Thackaringa Cobaltiferrous Pyrite Ore Samples,” Progress
Reports 1 – 4, Final Report.
Micron, 2004, “Bacterial oxidation test-work on the Pyrite Hill Cobalt Resource.”
Mineral Resources, 2004, “Appendix 3 Flotation Test Results.”
PIRSA, 2005, Primary Industries and Resources SA, www.pir.sa.gov.au.
Platsearch NL, 2004, “Annual Report 2004.”
Plimer, I.R., 1976, “Untilted Report regarding mineralogy of Big Hill/Pyrite Hill.”
Rio Tinto Exploration Pty Limited, 1998, “EL4535 Thackaringa 1 and EL4536 Thackaringa 2.” Fifth
Annual Report 30/6/98.
Sherritt Gorden Mines, 1980, “Examination of Cobalt Concentrates and Ore Samples from Australia.”
So Co Ltd, 2002, “Test-work for Thackaringa Project.”
Stagg, R.N., 2005, ‘Thackaringa Cobalt Project Status of Bacterial Leaching Work.”
Stevens, B.P.J. and Burton, G.R., 1998, “The Early to Late Proterozoic Broken Hill Province, New
South Wales.” AGSO Journal of Australian Geology and Geophysics, 17(3), 75 – 86.
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Vince Gauci Mining Consultants, 1992, “Review of the Pyrite Hill - Big Hill Cobaltiferous Pyrite
Deposits.”
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GLOSSARY OF TECHNICAL TERMS
Acid volcanics
Volcanic rocks with high content of quartz
Adit
A near horizontal tunnel with at least one end opening to the surface
Aeromagnetic survey
A survey made from the air to record the magnetic characteristics of rocks
Airborne EM (AEM)
A survey made from the air to record the electromagnetic characteristics of
rocks
Air-core
Percussion drilling method which can produce core
Albitic
Of or related to albite feldspar
Alteration
A change in mineralogical composition of a rock commonly brought about by
reactions with hydrothermal solutions or by pressure changes
Amphibolite
A crystalline rock containing mainly amphibole and plagioclase with little or
no quartz
Anomalous
A departure from the expected norm. In mineral exploration this term is
generally applied to either geochemical or geophysical values higher or lower
than the norm
Basalt
A fine grained volcanic rock composed primarily of plagioclase feldspar and
mafic minerals
Base metal
A non-precious metal usually refers to copper, zinc, lead, and nickel
Base of oxidation
Level beneath surface below which rocks are not affected by surface
weathering processes
Basement
Bedrock
Basic
Igneous rocks with low silica content
Bedrock
Solid rock underlying unconsolidated material
Bias
A tendency for measured results to deviate from “true” results
Bioleach
An ore processing method that uses bacteria to oxidise material, usually
sulphides
Biotite
A dark coloured mica mineral
Blank
A sample sent to a laboratory to test for cross contamination. A blank
contains none of the element being analysed
BLEG
Bulk leach extractable gold
Breccia
A rock consisting of angular fragments in a finer grained matrix
Broken Hill-type
A model for ore deposits with similar characteristics to the giant Broken Hill
lead-zinc-silver deposit
Bulk Density
The weight of a material divided by the volume it occupies (including pore
spaces)
Bulk leach
A laboratory technique whereby a sample is treated with a leaching agent
(i.e. cyanide) to extract a particular mineral
Calcine
To heat a material to drive off a volatile matter
Calcrete
A calcareous hard crust formed at or near the surface of soil by weathering
Calc-silicate
A metamorphic rock consisting mainly of calcium-bearing silicates such as
diopside and wollastonite, and formed by metamorphism of impure limestone
or dolomite
Cambrian
The period in geological time between 530 and 460 million years ago
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Carbonaceous
Rich in carbon/organic matter
Carbonate
Rock or mineral composed of more than 50 percent carbonate minerals such
as limestone or dolomite
Carboniferous
Geological time period from about 345 to 280 million years ago
Chalcopyrite
A copper iron sulphide mineral, the most important ore of copper
Chemical analysis
Accurate laboratory determination of the concentration of a given element in
a sample
Chemical symbols
Au – gold, Cu – copper, Zn – zinc, Pb – lead, As – arsenic, Ag – silver, NaCN
– sodium cyanide
Chert
Very fine grained rock composed of silica
Chlorite
A green plate iron-magnesium rich silicate mineral
Cobaltiferous
Containing cobalt
Collar
The starting point of a drillhole
Colloform
A texture, often found in certain types of mineral deposits, where crystals
have grown in a radiating and concentric manner
Conductivity
Geophysical anomaly relating to electrical conductivity often associated with
sulphides
Costean
A trench
Country rock
Term applied to rock surrounding or penetrated by mineral veins
Cut-off
A grade value above which material is usually ore and below which material
is usually waste
Density probe
A geophysical device used to measure the density of rocks in drillholes
Devonian
A period of geologic time between 345 and 395 million years ago
Diamond drilling
Method of obtaining a cylindrical core of rock by drilling with a diamond
impregnated bit
Diamond tail
The end part of a drillhole drilled using diamond coring, the start of the
drillhole is drilled using percussion methods
DigHEM
Digital Helicopter Electromagnetics, a proprietary airborne electromagnetic
survey system
Dip
The angle at which a rock layer, fault, or any other plane or surface is
inclined from the horizontal
Disseminated
Fine particles of mineral dispersed through the enclosing rock
Dolerite
A mafic intrusive rock
Dolomite
A sedimentary rock consisting mainly of the mineral dolomite (a calcium and
magnesium carbonate)
Duplicate
A duplicate sample or analysis is performed to measure precision
Dyke
Narrow body of igneous rock cutting across structure of the adjacent country
rocks
Eastman multishot camera
A device used to measure the azimuth and inclination of drillholes
EL
Exploration License in New South Wales
ELA
Exploration License application in New South Wales
Electromagnetic survey
EM - a geophysical exploration method based on measuring magnetic fields
using artificially induced currents into the ground
Epithermal
A low pressure and temperature hydrothermal deposition of minerals
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Euhedral
Perfect crystalline form of a mineral
Facies
The aspects of a rock unit reflecting the conditions of its origin
Fault
A fracture in rocks along which there has been relative movement either
vertically or horizontally
Feldspar
A group of aluminium silicate rocks that are very common in the Earth’s crust
Felsic
Light coloured rock containing an abundance of any of the following:feldspars, felspathoids and silica
Fence
A linear series of drillholes, often inclined and overlapping
Ferruginous
Containing iron
Float
Rock material dispersed from bedrock
Flotation
A method for separating and concentrating ores
Fold
A bend in strata or in any planar structure
Fold axis
The centre line of a fold
Foliation
Parallel orientation of platy minerals
Footwall
The underlying side of a fault, orebody or mine workings
Fragmental tuff
A rock formed by volcanic processes and containing fragments greater than
two centimetres
Fresh
Rock that has not been oxidised
g/t (ppm)
Grams per tonne (parts per million), a measure of precious metal content in a
sample
Galena
A mineral, lead sulphide, the dominant ore mineral of lead
Geochemical anomaly
The occurrence of higher than average content of an element in rock or soil
Geochemistry
Study of variation of chemical elements in rocks or soils
Geophysical exploration
The exploration of an area in which physical properties (eg. resistivity,
gravity, conductivity, magnetic properties) unique to the rocks in the area are
quantitatively measured by one or more geophysical methods
Geotechnical
Of or relating to the science of rock mechanics
Gneiss
Applied to banded rocks formed during high-grade regional metamorphism
(also gneissic)
Gossan
A surface capping of oxides of iron from the weathering of metallic sulphide
minerals
Grade
Quantity of ore or mineral relative to other constituents, in a specified
quantity of rock, usually expressed as ppm, ppb, g/t, lb/t or %
Granite
A coarse grained igneous rock which contains 20 – 40% quartz
Granodiorite
A coarse grained acid igneous rock, similar to granite but with a lower
percentage of silica
Greenschist facies
A grade of metamorphism referring to the amount of temperature and
pressure rocks were subjected to
Greywacke
A grey indurated sandstone consisting of poorly sorted grains of quartz,
feldspar and rock fragments in a clay matrix
Grid
A systematic array of points or lines
Hangingwall
The overlying side of a fault, orebody or mine workings
Hematite
A mineral composed of iron oxide; one of the most common ores of iron
Hornfels
A fine to medium grained rock produced by thermal metamorphism
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Hydrometallurgy
The treatment of ores by methods involving dissolution
Hydrophilic
Having a strong affinity for water
Hydrothermal
A process of ore formation in which minerals are deposited from hot aqueous
solutions
Igneous
A rock that has solidified from molten material or magma
Indicated
In reference to a mineral resource this is the second to lowest resource
confidence classification under the JORC code
Induced Polarisation (IP)
A surface electrical, geophysical surveying technique
Inferred
In reference to a mineral resource this is the lowest resource confidence
classification under the JORC code.
Intermediate
Igneous rocks whose composition is intermediate between acid and mafic
rocks
Intrusion/Intrusive
A body of igneous rock that invades older rocks.
Ironstone
A rock with large amounts of iron compounds.
Jarosite
An iron sulphate compound resulting from oxidation (weathering or leaching)
Jasper
An iron-rich siliceous rock.
JORC (Code)
Joint Ore Reserve Committee of the Australasian Institute of Mining and
Metallurgy. The JORC Code provides mandatory reporting requirements for
statements of Mineral Resources and Ore Reserves by Competent
Person(s). Most recently published in 2004
Laterite
Highly weathered residual material rich in secondary oxides of iron and/or
aluminium
Lava
A general term for molten rock that is extruded onto the surface
lb/t
Pounds per metric tonne, 1 lb/t is equal to 454.5 g/t or ppm
Leaching
The dissolution of mineral components in rocks and ores by bacteria, acids
or other reagents. Can be carried out in heaps, tanks or pressure vessels
Limb
Those parts that form the flanks of folded rocks
Limestone
A sedimentary rock consisting mostly of calcium carbonate
Limonite
A general term for a yellow to brown-black iron oxide minerals which are a
common weathering product
Lineament
A linear feature of regional extent, generally recognisable in the topography;
commonly detected by satellite imagery
Lineament
A large-scale linear feature as evidenced by topography, which may
represent underlying structural features
Lithology
A term pertaining to the general characteristics of rocks. It generally relates
to descriptions based on hand sized specimens and outcrops rather than
microscopic or chemical features
Lode
A tabular or vein like deposit of valuable mineral between well defined walls
of country rock
Long-section
A section projection parallel to the long axis of a body
Ma
An abbreviation for one million years ago (Megannum)
Mafic
Descriptive of rocks composed dominantly of magnesium and iron rockforming silicates
Magnetic survey
A geophysical technique which measures variations in earths magnetic field
Magnetite
A magnetic iron oxide mineral
Page 38
FINAL
Manganese
Manganese
Massive Sulphide
Any mass of abundant metallic sulphide minerals, usually of zinc, lead,
copper, iron and related to volcanism
Measured
In reference to a mineral resource this is the highest resource confidence
classification under the JORC code
Melnikovite
A finely layered iron sulphide mixture which includes pyrite
Mesh fraction
A sizing system used to screen samples prior to their chemical analysis
Mesothermal
Hydrothermal mineral (deposit) formed in the 200-300 degree range and at
depth
Metallurgy
The science that deals with procedures used in extracting metals from their
ores
Metamorphic rocks
The process by which changes are brought about in earth’s crust by the
agencies of heat, pressure and chemically active fluids
Metasediments
Sediments that have been metamorphosed
Mineral Resource
A concentration or occurrence of material of intrinsic economic interest in or
on the Earth’s crust in such form and quantity that there are reasonable
prospects for eventual economic extraction
Mineralisation
A concentration of metals and their chemical compounds within a body of
rock
ML
Mining Lease
mm
Millimetre, 0.001 metres
mRL
metres reduced level, the elevation in metres based on a datum
Mt
Abbreviation for million metric tonnes or 1,000,000 t
NQ
A standard diamond drill core size, 60.3 mm diameter
Open cut, open pit, pit
A mine worked at the surface
Ordovician
The period in geological time between 500 and 435 million years ago
Ore
Material that can be mined and treated at a profit
Ore Reserve
The economically mineable part of a Mineral Resource
Outcrop
The surface expression of a rock layer
Outlier
A statistical term for values that are outside the normal population of values
Oxidation (metallurgical)
Decomposing the structure of a mineral to allow further processing. Can be
carried out using heat, bacteria and acid
Oxidised (geological)
Decomposed by exposure to oxygen in the atmosphere and groundwater
(geological)
Palaeozoic
Era in geological history from the Pre-Cambrian to the Mesozoic or about
570 to 225 million years ago
Pegmatite
A coarse grained, igneous rock which often contains commercial minerals,
occasionally these are rare earth's
Pelite
The metamorphic equivalent of a mudstone or lutite
PEM
“Pulse electromagnetic” geophysical exploration technique
Percussion drilling
Method of drilling where rock is broken by the hammering action of a bit and
the cuttings are carried to the surface by pressurised air returning outside the
drill pipe
Permian
Period in geological history from about 286 to 248 million years ago
Petrographic
Pertaining to the optical study of rocks
Page 39
FINAL
PGE
Platinum group elements (includes platinum, palladium, ruthenium, and
rhodium)
Pit shell
The three-dimensional outline of an open pit or theoretical open pit
Plagioclase
A form of feldspar (see feldspar)
Pleistocene
One of the seven subdivision of the Tertiary period in the geological timescale
Polygonal estimation
A resource estimation method that applies polygons of influence around
drillholes
Porphyry
An igneous rock that contains conspicuous crystals in a fine-grained matrix
Porphyry copper
A copper deposit in which the copper minerals occur as discrete grains and
veinlets throughout a large volume of rock
ppb
Parts per billion (1,000 million)
Pre-Cambrian
The period of geological time prior to 540 million years ago (~=90% of all
time)
Pre-collar
The first part of a drillhole often drilled using percussion methods and then
finished with a diamond tail
Primary
Un-oxidised.
Proterozoic
The more recent period of the Pre-Cambrian
Psammite
The metamorphic equivalent of a sandstone or arenite
Pyrite
A common pale bronze iron sulphide mineral
Pyroclastic
Fragmental deposits formed from the accumulation of volcanic ejections
Pyrometallurgy
The treatment of ores by methods using high temperature
Pyrrhotite
A bronze coloured iron-sulphide
Quartz
Mineral species composed of crystalline silica
Quartzite
A silica rich metamorphic rock formed from sandstone
Quaternary
A period in geological time from 1.8 million years ago to the present day
RAB
Rotary air blast, a type of percussion drilling
Radiometrics
Geophysical technique measuring emission from radioactive isotopes
Replicate
Often refers to an additional laboratory analysis of a sample. Usually taken
randomly or as a check of unusual values
Reserve(s)
In-situ quantity of mineralised rock of known grade from which the contained
metal can be recovered economically taking into consideration, geological
mining, social, political, and environmental factors – see Ore, Ore Reserve,
JORC Code
Resistivity survey
A geophysical technique which measures the electrical resistance of rocks in
the ground
Resource(s)
In-situ quantity of mineralised rock of known grade, the extent of which has
been estimated on the basis of geological information and from which the
contained metal may be recoverable economically – see JORC Code
Reverse Circulation
RC drilling
A method of percussion drilling whereby rock chips are recovered by air flow
returning inside the drill rods rather than outside, thereby providing usually
reliable samples
Rhyolite
Fine grained acid volcanic rock
Roasting
Applying heat to achieve oxidation
Page 40
FINAL
Rock chip sample
A series of rock chips or fragments taken at regular intervals across a rock
exposure
Rutile
A mineral, TiO2
Sandstone
Sedimentary rock composed of sand-sized grains
Schist
A metamorphic rock with platy to foliated texture
Secondary enrichment
Enrichment of primary mineralisation, usually by weathering processes
Sedex
Sedimentary exhalative - a submarine volcanic process whereby sediments
or ore deposits are deposited on the sea floor
Sericite
Fine grained white micaceous mineral
Shaft
A long, narrow, vertical tunnel sunk into the earth
Shale
Fine-grained sedimentary rock with well defined bedding planes
Shear
A zone where lateral movement along parallel planes produces deformation
of rock
Silicification
The process whereby original rock minerals are chemically replaced by
various forms of silica
Siltstone
A fine-grained sedimentary rock composed largely of silt-sized particles
Silurian
Period of geologic time from about 440 to 410 million years ago
Sirotem
A proprietary electromagnetic survey technique
Skarn
A term to describe a contact metamorphic deposit in limestone
Slate
A compact fine-grained metamorphic rock
Soil sampling
Systematic collection of soil samples at different locations in order to study
the distribution of elements in the soil horizons
Solid solution
A homogeneous and stable solution of one solid substance in another
SP (self potential)
A geophysical technique which measures the natural earth currents at the
ground surface
Sphalerite
A zinc-iron sulphide mineral; a major economic source of zinc
Splitter
A device to reduce the size of a sample without introducing bias
Standard
A standard sample is a sample of known grade used to test a laboratories
accuracy
Stanniferous
Containing tin
Stockwork
A network of veins
Stope
Generally the hole left underground after mining narrow moderate to steeply
dipping veins
Stratabound
Said of a deposit confined to a single stratigraphic unit
Stratigraphy
The study of formation, composition and correlation of sedimentary rocks
Stream sediment sample
Drainage sample usually consisting of –80 mesh (small) fraction of active
stream silt and sediment
Strike
Horizontal direction or trend of a geologic structure
Stringer
A narrow vein of mineral traversing a rock mass of different composition
Sub-crop
Outcropping bedrock that is dislocated from the bedrock but has not been
transported
Sulphates
Minerals consisting of a chemical combination of sulphur with a metal
Sulphatising roasting
Roasting a material so that a sulphide material is oxidised to a sulphate form
Page 41
FINAL
Sulphides
Minerals consisting of a chemical combination of sulphur with a metal
Sulphosalts
A certain type of sulphur mineral distinct from sulphide minerals
Supergene
An enrichment or deposit formed by descending fluids in weathered rock
Syncline
A fold that is concave up, with younger rocks in the middle
Syngenetic
A mineral deposit which is said to have formed at the same time as the
enclosing rocks
Tailings
Reject products from a mineral treatment plant, usually finely crushed or
ground
TEM
A proprietary ground electromagnetic survey technique
Tertiary
The period of geological time between 65 and 1.8 million years ago
True thickness
The thickness as measured perpendicular to the plane of an object
Tuff
A rock composed of volcanic ash
Tuffaceous
A rock which contains pyroclastic material
Turbidite
A sedimentary rock formed by turbidity (density) currents along a sloping
ocean floor
Ultramafic
An igneous rock comprised chiefly of mafic minerals
Umpire assay
An assay sent to a laboratory, other than the one generally in use, as part of
a quality measurement programme
unit
The smallest division of a New South Wales exploration licence. A unit has
dimensions of 1° longitude by 1° latitude, or approximately 300 ha
UTEM
A proprietary ground electromagnetic survey technique
VHMS
Volcanic hosted massive sulphide - high grade and value deposits related to
silicic volcanism
VLF-EM
A ground geophysical survey technique utilising very low frequencies
Volcaniclastic
Sediments comprising rock fragments derived by explosion or eruption from
a volcanic vent
Volcanics
Collective term for extrusive igneous rocks
Water immersion method
A method for determining the density of a substances by measuring the
volume of water it displaces
Page 42
FINAL
SELECTED DRILLING RESULTS
Project
Hole Name
From
(m)
To
(m)
Interval
(m)
Cobalt
(lb/t)
Pyrite Hill
TH1
123.40
187.80
64.4
2.43
TH2
78.03
102.11
24.08
3.66
TH3
77.20
129.54
51.82
2.25
80PYH1
7.50
14.20
6.70
1.94
80PYH2
34.10
48.25
14.15
2.18
80PYH3
23.00
35.00
12.00
1.57
80PYH4
39.75
55.00
15.25
1.61
80PYH5
36.70
65.00
18.30
2.56
80PYH6
54.00
74.00
20.00
1.56
80PYH7
67.00
79.40
12.40
2.45
80PYH8
92.00
101.70
9.70
0.92
80PYH9
81.20
82.35
1.15
1.12
80PYH10
48.45
78.00
29.55
2.50
80PYH11
34.60
91.50
56.35
2.18
80PYH12
30.20
36.50
6.30
2.14
85.15
90.80
5.65
2.71
Big Hill
North East
80PYH13
52.20
54.20
2.00
1.12
80PYH14
251.80
273.40
21.60
2.76
MGM2
85.00
91.00
6.00
3.66
99.00
111.00
12.00
3.85
117.00
125.00
8.00
2.97
150.00
154.00
4.00
3.60
157.00
160.00
3.00
2.23
BH1
40.50
53.30
12.80
7.50
BH1
64.50
84.40
19.90
2.65
BH2
24.40
30.50
6.10
2.31
80BGH5
39.00
49.00
10.00
1.74
80BGH6
28.00
53.00
25.00
3.54
80BGH7
3.00
6.00
3.00
2.03
80BGH7
15.00
19.00
4.00
1.41
80BGH8
44.00
78.15
34.15
2.19
T98C03
68.00
73.00
5.00
3.70
T98C04
90.00
100.00
10.00
2.40
T98C05
35.00
52.00
17.00
2.00
T98C06
83.00
91.00
8.00
2.20
T98C07
35.00
46.00
11.00
3.40
T98C09
95.00
107.00
12.00
2.20
T98C10
101.00
110.00
9.00
1.90
T98C01
35 .00
71.00
35.00
2.10
13.00
32.00
19.00
1.50
Page 43

updated competent persons` report on the mineral assets of broken

Transcription

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