Document 6503344

Canadian Rockhound: How to tell minerals apart
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Contents:
Rocks & Minerals
How to tell Minerals Apart
By Marilyn Fraser
z What are they?
z Telling them Apart
z Mineral Identifier
z Classifying Rocks
z The Rock Cycle
z Igneous Rocks
Between 2500 and 3000 minerals have been
identified, but there are only 60 that you will
come across in the field. They are identified by
their various characteristics – colour, luster,
streak and hardness are the obvious ones.
Mohs Scale
Minerals:
z Metamorphic Rocks
z Sedimentary Rocks
Colour
Geology of the Earth
z Plate Tectonics
z Geological Time
Colour is an important key to identifying your
specimen – just as its important to be able to tell
an apple from a pear.
1 Talc
z Natural Disasters
Collections
z Starting a Collection
z Organizing
Field Trips
z Preparing
z Using Maps
Safety Tips
z Safe Rockhounding
z Code of Conduct
Luster
Another important thing to notice when
identifying a mineral is the shine – known as
luster – whether it looks like metal (metallic) or
glass, like diamond or silky.
Streak
2 Gypsum
3 Calcite
The streak made by a mineral is often a different
colour than the mineral itself. The streak is
found by rubbing the mineral on an unglazed
piece of ceramic tile. The colour of the streak is
important in helping you identify the mineral.
Clubs & Societies
z Directory
Back to
Front Page
Hardness
4 Fluorite
Another important factor in knowing your rocks
is the hardness. A common system of
measuring hardness is the Mohs Scale. The
scale runs fron the softest mineral, talc, as
"Mohs 1" to the hardest mineral, diamond, as
"Mohs 10". (The pictures to the right show what
these minerals look like).
The Mohs Scale:
1.
2.
3.
4.
5 Apatite
Talc
Gypsum
Calcite
Flourite
http://epe.lac-bac.gc.ca/100/201/300/cdn_rockhound/1997-2000/junior_minprop.html
05/02/2006
Canadian Rockhound: How to tell minerals apart
5.
6.
7.
8.
9.
10.
Apatite
Feldspar
Quartz
Topaz
Corundum
Diamond
In the beginning you can use four categories of
hardness:
z
z
z
z
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6 Orthoclase
softer than 2.5
between 2.5 and 5.5
between 5.5 and 7 and
harder than 7
Your fingernail has a hardness of 2.5. If you can
scratch your mineral or rock with your fingernail,
you know it is softer than 2.5. A pocket knife has
a hardness of 5.5 and quartz has a hardness of
7. If you can scratch it with your pocket knife,
you know it is softer than 5.5.
These four tests – colour, luster, streak and
hardness – will go a long way to help you
identify the mineral you find. All the mineral field
guide books around the world use these
characteristics in describing minerals.
7 Quartz
8 Topaz
Copyright ©1998 Marilyn Fraser
E-mail: [email protected]
This article may not be copied, distributed or
reprinted in any form without the author's
permission. To contact the author, please use
the e-mail address provided. If you are unable to
contact the author, please contact the Canadian
Rockhound. Authorized reprints must
acknowledge the author, original source and the
Canadian Rockhound, and include the website
URL address of the Canadian Rockhound.
9 Corundum
10 Diamond
Images of Mohs scale minerals are Copyright
©1995-1996 by Amethyst Galleries, Inc., and are used here for
educational purposes only.
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Canadian Rockhound: How to tell minerals apart
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Copyright © 2000 Canadian Rockhound
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