Mediterranean trade of the most widespread Roman volcanic

Journal of Archaeological Science 37 (2010) 2081e2092
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Journal of Archaeological Science
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Review
Mediterranean trade of the most widespread Roman volcanic millstones from
Italy and petrochemical markers of their raw materials
Fabrizio Antonelli*, Lorenzo Lazzarini
Laboratorio di Analisi dei Materiali Antichi (LAMA) e Dip. Storia dell'Architettura, Università IUAV di Venezia, San Polo 2468, 30125 Venice, Italy
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 29 October 2009
Received in revised form
6 February 2010
Accepted 15 February 2010
The petrochemical study of millstones can contribute to improve the archaeological research into
reconstruction of ancient communication routes and trade networks. Volcanic rocks are geographically
restricted and rather rare in the Mediterranean regions, and during the Roman period Italian volcanoes
were important sources of raw materials for millstones, so the task of determining their geological origin
is relatively straightforward. The Italian vesicular volcanics most frequently employed for this purpose
were: trachytes from Euganean Hills (Veneto), leucite-bearing lavas from the Vulsini Volcanic District
(Latium), basic-intermediate leucite-bearing lavas from Somma-Vesuvius (Campania), silica undersaturated lavas from Monte Vulture Volcano (Basilicata), a rhyolitic ignimbrite from Sardinia and basic
products from Mount Etna and the island of Pantelleria (Sicily). This paper contains a general outline of
the trade network for each volcanic typology used for millstones during the Roman period e updated
with data concerning the leucite-bearing lavic items discovered in the archaeological sites of the ancient
Cuicul (now Djemila, Algeria) e together with a summary of their petrographic and geochemical features.
Ó 2010 Elsevier Ltd. All rights reserved.
Keywords:
Mediterranean trade
Italy
Algeria
Cuicul
Roman millstones
Lavas
Petrography
Provenancing
1. Introduction
It is generally acknowledged that archaeometric research on
mills and millstones found in the Mediterranean area is an
important means for the identification of the production sites of
these artefacts and for the rediscovery of important trade networks
of protohistory and history. During the Roman age, hourglassshaped or flat, cylindrical rotary millstones were exported to and
imported from many provinces of the Empire, including Germany,
France, Italy, Spain, Portugal, Morocco, Tunisia, Libya, Algeria,
Cyprus and Turkey (cf. Williams-Thorpe, 1988; Antonelli et al.,
2001, 2005 and bibliography therein). Most of these Roman millstones discovered in archaeological sites throughout the Mediterranean are made of volcanic rock. In fact, lavas are generally wearresistant and they are particularly suitable for milling because of
their abrasive property (hard enough not to contaminate the flour
unduly) and rough vesicular surface that provides a good grinding
capacity. The mills most commonly used by the Romans were up to
1.5 metres high (Fig. 1) and typically consisted of an hourglassshaped (double-cone) upper stone (catillus) resting on the conical
lower stone (meta) (Moriz, 1958). The catillus was turned on the
meta by means of a bar pushed by slaves or a donkey (mola asinaria
* Corresponding author.
E-mail address: [email protected] (F. Antonelli).
0305-4403/$ e see front matter Ó 2010 Elsevier Ltd. All rights reserved.
doi:10.1016/j.jas.2010.02.008
or iumentaria; donkeymills). As proposed by Antonelli et al., 2001,
re-interpreting Varro (the Latin scholar of the first century BC)
rotary millstones (molae versatiles) were most probably invented
(no later than the fourth century BC) in Volsinii veteres (present-day
Orvieto), the famous Etruscan village, and not simply in Volsinii
(or Volsinii novi, now Bolsena), the Roman city built in the first half
of the third century BC close to Bolsena Lake, ca 8 km NE of Orvieto.
Rotary millstones hourglass-shaped are also known as Pompeianstyle millstones after the site where they occur so frequently and
were first discovered (i.e. Pompeii-Naples; Peacock, 1989; Buffone
et al., 2003). Other famous Italian archaeological sites where
well-preserved examples have been discovered include Ostia
Antica (Rome) and Aquileia (Udine). They were a very popular item,
highly prized in Roman bakeries and military settlements of the
Imperial provinces. Shipwrecked cargoes of millstones such as that
of Sec (Mallorca, Spain; Williams-Thorpe and Thorpe, 1990), testify
both to their importance in the Roman period and to the fact that
they were traded throughout the eastern and western Mediterranean. Fortunately, seeing that volcanic complexes occur in few
regions of the Mediterranean basin, volcanic rocks exploited for
millstones may be very important markers for reconstruction of
ancient commercial and communication routes. Old and recent
works (Peacock, 1980, 1986, 1989; Ferla et al., 1984; WilliamsThorpe, 1988; Williams-Thorpe and Thorpe, 1989, 1990, 1991,
1993; Lorenzoni et al., 1996, 2000a,b; Oliva et al., 1999; Antonelli
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F. Antonelli, L. Lazzarini / Journal of Archaeological Science 37 (2010) 2081e2092
Table 1
Whole rock major oxides (wt%) and trace elements (ppm) analyzed for Roman lavic
millstone D, D3, D4 discovered in the archaeological site of the ancient Cuicul
(Djemila, Algeria). An average (OR-AV) of 11 analyses (of leucite phonolite lavas from
the Orvieto quarries (after Antonelli et al., 2001) is reported for the purposes of
comparison. Standard-deviation (s) of the average values OR-AV with respect to the
quarry samples of Antonelli et al. (2001) are also reported. Analyses were performed
at the ALS Chemex Laboratory Group (Vancouver, Canada) by ICP-OES-MS methods.
Errors were 1% for major oxides and 5% for trace elements.
Fig. 1. Classical Pompeiian-style millstones. (a) Pistrinum of Pompeii; (b) Aquileia,
Archaeological Museum; (c) Pistrinum of Ostia Antica.
et al., 2000, 2001, 2004, 2005; Renzulli et al., 2002a; Santi et al.,
2004; Buffone et al., 2003) have combined to establish a useful
petrographic, geochemical and historical database on the source
areas for the grinding tools used in Mediterranean countries from
the Neolithic to the Roman periods.
The purpose of this paper is to give a concise overview of the
main Italian volcanic rocks exploited by the Romans in the manufacture of exported millstones as well as of their trade network. The
general outline is updated with new data referring to leucite
phonolite mills discovered at the archaeological site of ancient
Cuicul (now Djemila, Algeria) (cf. Figs. 4e6 and Table 1).
2. Quarrying areas and circulation of the artifacts
The Romans exploited several Italian lava sources (Fig. 2),
generally vesicular and so relatively easy to work, to produce
millstones and rotary querns; judging by the archaeological finds
the most widespread were (from northern to southern Italy): (i)
Na-trachytes from the Euganean Hills (Padua e Veneto); (ii) leucite
phonolites from quarries in the Vulsini Volcanic District (near
Orvieto e Latium); (iii) leucite basaltic trachyandesites of SommaVesuvius (Naples e Campania) and (iv) tephrites-foidites from
Vulture (Potenza e Basilicata); (v) volcanic rocks from Sardinia,
Sample
D
D3
D4
OR-AV
s
wt%
SiO2
Al2O3
Fe2O3
MnO
MgO
CaO
Na2O
K2O
TiO2
P2O5
LOI
55.20
20.00
4.37
0.16
0.83
3.84
2.98
8.48
0.53
0.13
2.86
54.60
18.60
3.77
0.14
0.71
4.86
3.27
8.25
0.47
0.16
2.85
54.00
19.85
3.41
0.13
0.79
4.91
2.63
10.55
0.41
0.25
2.78
56.35
21.42
4.37
0.13
0.81
3.57
2.79
9.95
0.50
0.10
e
0.36
0.13
0.15
0.01
0.03
0.09
0.42
0.30
0.02
0.01
e
Total
99.38
97.68
99.71
99.99
e
K2O/Na2O
2.85
2.52
4.01
3.57
e
ppm
V
Cr
Co
Ni
Rb
Sr
Y
Zr
Nb
Ba
La
Ce
Nd
Sm
Gd
Dy
Er
Yb
Lu
Hf
Th
143
<10
6.50
<5
278
2100
39
811
54.1
2300
204
394
121
18.05
17.00
8.17
4.61
4.05
0.57
13.10
144
120
<10
5.70
<5
282
2170
35
649
48.0
2430
183
316
108
16.05
15.00
7.20
4.22
3.64
0.52
11.60
126.5
114
<10
5.80
<5
396
1865
30
558
36.6
2120
144
255
87
13.10
12.15
6.04
3.38
2.96
0.42
9.50
95.6
125
2.67
5.56
4.00
352
1947
39
730
45.0
2232
183
325
107
16.10
11.30
7.18
3.42
3.35
0.51
10.80
160
19.45
1.0
0.3
0.9
40.0
61.0
1.6
69.0
1.9
44.0
7.0
12.0
4.0
0.50
0.60
0.32
0.13
0.12
0.02
0.40
9
chiefly rhyolitic ignimbrite from Mulargia and, to a very minor
extent, the grey vesicular subalkaline basalts from different parts of
the island (not considered here); (vi) hawaiites, mugearites and
basalts from Etna (Catania e Sicily) as well as, to a minor extent,
some other Sicilian basic lavas from Hyblean Plateau and the
islands of Pantelleria, Ustica and Lipari. However, according to the
archaeological and archaeometric evidence, volcanics (iii), (v) and
(vi) were generally preferred by Romans for export on a mediumlarge scale, (i)e(ii) were exported on a medium-to-small scale,
whereas the lavas from Vulture (iv) were seldom transported far
from the production centres and basically employed locally and on
a small scale.
2.1. Trachytic rocks from the Euganean Hills e Venetian Volcanic
Province
The Euganean Hills, located in North-Eastern Italy (province of
Padua) within the Venetian Tertiary Volcanic Province, comprise 81
domes whose origin is related to the extensional tectonic regime of
the South-Alpine foreland (De Pieri et al., 1983) and the extensive
eruptive activity that took place from the late Paleocene to the late
F. Antonelli, L. Lazzarini / Journal of Archaeological Science 37 (2010) 2081e2092
2083
Fig. 2. Geographic location of the main Italian volcanic rock source areas exploited by the Romans to manufacture millstones. 1. Euganean Hills: general map after Capedri et al.,
2000. Letters and numbers in bold are related to the sites chemically analyzed by Capedri et al., 2000. 2. Roman Magmatic Province: draft of the outcrops and exploited sources of
volcanic products (after Buffone et al., 2000, modified). 3. Sardinia: sketch map of showing the distribution of OligoceneeMiocene (diagonal lines) and PlioceneePleistocene
(stippled areas) volcanic rocks (after Williams-Thorpe and Thorpe, 1989; modified). 4. Mt. Etna Volcano: sketch map showing the distribution of the main units (after Cristofolini
et al., 1991, modified). (1) Sedimentary basal levels; (2) Tholeiites; (3) Ancient Na-alkalic deposits (basalts and hawaiites dating back to 225 ky before present); 4) Trifoglietto Unit
(mugearites); (5) Detrital alluvial fan originated from the Valle del Bove; (6) Elliptical volcano deposits (Mongibello Unit; hawaiites to trachytes); (7) Recent Mongibello (hawaiites
and mugearites); (8) Edge of the Valle del Bove; (9) Major faults.
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F. Antonelli, L. Lazzarini / Journal of Archaeological Science 37 (2010) 2081e2092
Oligocene. Volcanic and sub-volcanic products range from subordinate basalts to intermediate and acidic lithotypes, mostly
trachytes and rhyolites with a moderate Na-alkaline magmatic
affinity. The latter crop out in the central part and at the edge of the
area respectively and testify to the change in magmatic activity in
the Lower Oligocene (Zantedeschi, 1994). Euganean Trachytes have
been among the most widely distributed stones of NE Italy since
ancient times. They were already used by the Paleo-Venetian
populations in the seventh century BC for stelae (preserved in the
Archaeological Museums of Este and Padua) and mills (Antonelli
et al., 2004). The Romans occupying the Po Valley from the
second century BC used it much more abundantly for the same
purposes and for architectural elements (columns, capitals, lintels,
pillars, etc.), water pipes, bridges and to pave Venetian, Istrian and
Emilian roads (several sections of the Via Aemilia were paved with
polygonal trachytic blocks; Renzulli et al., 1999, 2002b). In Roman
times the stone also reached distant towns such as Ticinum (Pavia)
(Tozzi and Oxilia, 1981), Mediolanum (Milan), Tergeste (Trieste),
Fanum Fortunae (Fano; Renzulli et al., 1999) and Ankon (Ancona;
Renzulli et al., 1999): these towns form a triangle within which
trachyte is very often found. In the same period, Euganean trachytic
millstones and rotary-millstones were manufactured and spread
throughout the X Regio Augustea, Venetia et Histria (Antonelli et al.,
2004; Antonelli and Lazzarini work in progress) also reaching some
localities of ancient Aemilia and Picenum (Marche) regiones (i.e.,
Fossombrone and Urbisaglia e Renzulli et al., 2002a; Santi and
Renzulli, 2006). Among the 70 open-pit trachyte quarries identified in the field by Capedri et al. (2000), the sites where exploiting
activity was particularly important were Monselice, Monte Rosso,
Monte Oliveto, Monte Merlo, Monte Lispida, Monte Alto and Monte
Altore (Fig. 2). The trade towards the south was quite easy to carry
out (especially from the Monselice area) along the Mid-Adriatic
coast and also throughout a system of drainage channels joining the
hills to the paleo-Adige and the Brenta Rivers (Renzulli et al., 1999,
2002b), while the connections between Euganean sources and the
regions to the east could be effected by using the fluvial and
maritime routes that had operated in this part of Caput Adriae since
protohistoric times.
2.2. Leucite phonolite from Orvieto e Vulsini Volcanic District
In the Mediterranean area, the use of leucite-bearing lavas was
particularly widespread. Millstones and rotary querns produced
from these lavas have been discovered in Italian archaeological
sites (e.g., Aquileia e unpublished data e Luni, Veio, Ostia,
Ercolano, Pompeii, Paestum and in Sicily; Antonelli et al., 2001;
Santi et al., 2004 and bibliography therein) as well as in other
Mediterranean regions such as Iberia, France, Cyprus, Tunisia,
Tripolitania, Cyrenaica (Peacock, 1980, 1986; Williams-Thorpe,
1988; Oliva et al., 1999; Antonelli et al., 2001, 2005) and Algeria
(Djemila, ancient Cuicul; new data included in this work). On the
basis of fieldworks and archaeological studies Peacock (1980,
1986) concluded that the main quarry and production centre of
leucite-bearing Roman millstones was located close to Orvieto
(between Sugano and Buonviaggio; Fig. 2) in the Vulsini Volcanic
District (0.6e0.125 Ma; Nappi et al., 1998; Peccerillo, 2005). The
first detailed petrographic and geochemical database on this
quarry with a clear archaeometric goal was created by Antonelli
et al. (2000, 2001). The data confirmed Peacock's suggestion and
revealed the local use of this rock for some oval saddle-querns
already in the ninth century BC. Later on, several petro-archaeometric works (Renzulli et al., 2002a; Buffone et al., 2003; Santi
et al., 2004; Antonelli et al., 2005) showed unequivocally that
the leucite phonolite quarried near Orvieto is the most widely
used lava for manufacturing millstones in the Roman period. It
was also inferred (Antonelli et al., 2001) that at ca 10 km ESE of
the Orvieto quarries, at the confluence of the Tiber and Paglia
Rivers, the fluvial port of Pagliano was the main collecting point
for the millstone trade (they were probably shipped as ballast with
wheat loads) along the River Tiber. This latter was a natural fluvial
waterway which enabled the Orvieto artefacts to be transported
down to the Tyrrhenian Sea (Pavolini, 1986; Antonelli et al., 2001;
Renzulli et al., 2002a). Similarly, the port of Ostia Antica, located at
the estuary of the River Tiber, probably represented the starting
point of the leucite phonolite millstones for their journeys along
the different Mediterranean routes.1 The strategic position of the
quarries and the high grinding performance of these rotary
millstones (due to the high vesiculation and intrinsic abrasive
capacity of the mineralogical assemblage of the rock as well as to
its durability) only partially explains why they were so frequently
exported to faraway provinces of the Roman Empire, also to places
where fairly similar lavas outcrop and were used to produce the
same items most likely cheaply because of lower transportation
costs (i.e. Pompeii). Probably, apart from commercial reasons, this
important trade involving the pistrina of all the western Mediterranean (Fig. 3a) depended on historical and symbolic aspects
related to the renown of the place where this kind of millstone
was invented.
2.3. Leucite basaltic trachyandesites from Castello di Cisterna
quarry e Somma-Vesuvius Complex
The leucite-bearing lavas from the Somma-Vesuvius, specifically those outcropping and exploited close to Castello di Cisterna
(Naples; Fig. 2), were indicated as the probable rock used for the
hourglass millstones of ancient Pompeii from the end of the
nineteenth century (Tenore, 1883). One century later, Peacock
(1980, 1989), basing his opinions both on hand specimens and
typological comparison with volcanic millstones from Orvieto
found at Ostia, was the first to suggest that only a part of those
discovered at Pompeii were made from the Vesuvius raw materials. More recently, Buffone et al. (2000, 2003), in the first
detailed archaeometric studies of this topic, stated that more than
60% of the Pompeiian hourglass millstones were produced at
Orvieto (infra) while fewer than 40% are made of local leucite
basaltic trachyandesites belonging to the oldest eruptions of
Somma-Vesuvius (30 ka ago; Peccerillo, 2005; these products are
almost wholly covered by the younger volcanic formations) and
cropping out at Castello di Cisterna (near the Circumvesuvius
railway station) and outside the walls of Pompeii, east of the
Amphitheatre. They also pointed out that these volcanic rocks
correspond to the so-called ottavianiti of Johansen (1937), a name
nowadays no longer used. Working from the suggestion of Sebesta
(1974) on the presence at Aquileia of Somma-Vesuvius rock millstones, Buffone et al. (2003), on the basis of a morphological
examination of the mills conducted simply on the pictures
annexed to the Sebesta
paper, stated both that Vesuvius must have
been an export area for millstones and that there must have been
a trade route for these items from Naples to Aquileia (UD e Friuli).
We are currently carrying out a detailed petrographic and
geochemical study on the Aquileia millstones. However, there is so
far no significant archaeological-archaeometric evidence to
support this conclusion or to suppose the existence of trade on
a large or medium scale. In fact, hourglass millstones from this
region have been found only in Campania and at Grumentum
(Basilicata; Lorenzoni et al., 2000a,b).
1
We underline that all the rotary-millstones present in the big bakery of Ostia
Antica come from Orvieto (Santi et al., 2004).
F. Antonelli, L. Lazzarini / Journal of Archaeological Science 37 (2010) 2081e2092
2085
Bronze Age to Roman times and beyond, but use and export of these
items were just regional (Lorenzoni et al., 1996, 2000a,b). Roman
millstones made of tephrite-foiditic lavas from Vulture have been
detected in a few Roman sites of the southern Italian mainland, e.g.,
Basilicata, Molise and Apulia regions (i.e., Egnatia, S. Giovanni di
Ruoti, Biferno Valley, Cannae, Altamura Gravina di Puglia; Volterra
and Hancock, 1994; Lorenzoni et al., 2000a,b; Williams-Thorpe,
1988; Volterra, 1997). They are only of the Olynthian hopperrubber type and, following Lorenzoni et al. (1996), were manufactured in several (unknown) localities scattered on the outcropping
area of the small flows of the vesicular lavas, particularly on the
north-eastern and south-eastern slopes of the volcano. The same
authors found excavation signs on tephrite blocks between the
villages of Melfi and Rapolla.
2.5. Rhyolitic ignimbrite from Mulargia (Sardinia)
Fig. 3. (a) Geographic distribution of leucite phonolite millstones from Orvieto, inferred
through detailed petrological studies (full circles) or hand specimens/quick petrography
(asterisks). The Orvieto production centre (here located as a stylized rotary millstone)
and the River Tiber (bold line in central Italy) are also located. 1. Cyrene and 2. Leptis
Magna (Libya; Antonelli et al., 2005); 3. Sabratha (Libya; Antonelli, unpublished data); 4.
El Djem and 5. Carthage (Tunisia, Peacock, 1980); 6. Cuicul (Djemila, Algeria; present
study); 7. Palermo (Williams-Thorpe, 1988); 8. Halaesa (Peacock, 1980); 9. Grumentum
(Lorenzoni et al., 2000b); 10. Paestum (Peacock, 1980, 1989); 11. Pompeii (Peacock, 1989;
Buffone et al., 2003); 12. Herculaneum (Peacock, 1980, 1989); 13. Mondragone
(Williams-Thorpe, 1988); 14. Biferno Valley (Williams-Thorpe and Peacock, 1995); 15.
Ostia (Santi et al., 2004); 16. Anguillara (Peacock, 1986); 17. Veii (Peacock, 1980); 18.
Suasa (Santi et al., 2004); 19. Fossombrone (Renzulli et al., 2002a); 20. S.Angelo in Vado
(Antonelli et al., 2001); 21. Colombarone (Santi et al., 2004); 22.Pesaro (Antonelli et al.,
2001); 23. Lucca (Peacock, 1989); 24. Luni (Peacock, 1980); 25. Cannetolo di Fontanellato
(Santi et al., 2004); 26. Concordia (Donner, 1993); 27. Aquileia (unpublished data; work
in progress); 28. Magdalensberg, Klagenfurt (Carinthia; T. Gluhak, personal communication); 29. Carnuntum / Bad Deutsch-Altenburg (Austria; T. Gluhak, p.c.); 30. Les
Martys (Oliva et al., 1999); 31. Empuries; 32-35. Badalona, Barcelona, Carthagena, Zaragoza (Gimeno et al., 2010); 36. Astorga (Peacock, 1986, 1989); 37e38. Nea-Pafos &
Nicosia, Cyprus island (Antonelli, quick petrography) (b) Geographic distribution of
Sardinian ignimbrite millstones from Mulargia (here located as a stylized rotary millstone) in the Western Mediterranean area. After Williams-Thorpe and Thorpe, 1989,
modified. 1. Ampurias; 2. Tetouan musum; 3. Pollentia (Mallorca; Williams-Thorpe and
Thorpe, 1991) 4e10. Sassari; San Pietro di Sorres; Sant'Elena; Monte Zuighe; Sa Pattada;
Mulargia; Tharros; 11. Segesta; 12. Solunto; 13. Megara Hyblea; 14. Selinunte; 15. Utica;
16. Carthage; 17. Musti; 18. Sousse Museum; 19. Gightis; 20. Cuicul (Djemila, Algeria;
Antonelli and Lazzarini, quick petrography); 21. Volubilis (Morocco; Antonelli and
Lazzarini, quick petrography).
2.4. Tephrites-foidites from Vulture (Potenza e Basilicata)
The Mount Vulture is an extinct volcano, mid-Pleistocene in age
(De Fino et al., 1986), rising on the southern Apennine Chain
(northern Basilicata; Fig. 2) and representing the easternmost
magmatic event occurring during the Quaternary in centralsouthern Italy. It was an active millstone producing area from the
Sardinia was an important millstone production centre and
a source of millstone trade during the period of Roman settlement.
Studies of Roman millstones on the island showed that the
Pompeiian type is the most common, whereas cylindrical hand
querns occur more rarely (Peacock, 1980; Williams-Thorpe and
Thorpe, 1989). The great majority of these items are made of
a distinctive reddish rhyolitic ignimbrite and, to a very minor
extent, of grey vesicular lavas of basic-intermediate composition.
Following Williams-Thorpe and Thorpe (1989), there are several
areas on the island where archaeological, historical and local
tradition indicate a possible millstone production in the past. In
particular, the rhyolitic millstones are from a single source of
Oligocene-Miocene ignimbrite cropping out at Mulargia (called
Molaria in Roman times; Meloni, 1975), a village near Macomer
(west-central Sardinia; Fig. 2), while the millstones made of intermediate-basic lavas have varied sources within Tertiary and, above
all, PlioceneePleistocene volcanics, i.e.: Monte Arci (west Sardinia),
ca 30 km south of Oristano; Monte Teccu, in the south-eastern
sectors of the island; Montiferro and Punte Luzzanas (west-central
Sardinia), southwest of Macomer; Orroli and Nurri (southern
Sardinia), ca 50 km north of Cagliari and some others. However, on
the basis of the archaeometric studies (Peacock, 1980; WilliamsThorpe, 1988; Williams-Thorpe and Thorpe, 1989) we can
conclude that, starting from the 1st century AD, only the Mulargia
millstone production area is clearly proven as a major source and
shows clear evidence of significant Roman trade, whereas
millstones from all the other Sardinian localities (e.g., the subalkaline basalts from Monte Arci) were merely exploited locally or
regionally during the Roman period. Mulargia millstones, almost
exclusively hourglass-shaped, were widely exported in the western
Mediterranean (particularly towards North-Africa) from Morocco
(Volubilis e unpublished data e and Tetouan; Williams-Thorpe,
1988; Williams-Thorpe and Thorpe, 1989) to Sicily (Segesta,
Solunto, Selinunte and Megara Iblea) passing through Spain
(Ampurias and Mallorca), Algeria (Djemila e unpublished data),
and Tunisia (Utica, Carthage, Musti, Sousse and Gightis; WilliamsThorpe and Thorpe, 1989). Peacock (1980) first supposed a trade
in millstones between Sardinia and North Africa from the Roman to
Byzantine periods remembering also that the island was under the
control of Carthage during the Vandal period. This trade (partially
and indirectly confirmed also by the presence of columns made of
Sardinian pink granite in many of the above-mentioned sites)
generally shows a steep fall in the frequency of occurrences as the
distance from Sardinia increases (Williams-Thorpe and Thorpe,
1989); since this assumption does not appear to apply to
Carthage, where a significant number of Pompeiian millstones
made of Sardinian red-brown ignimbrite were found, WilliamsThorpe (1988) suggested that the town had a role as importer
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F. Antonelli, L. Lazzarini / Journal of Archaeological Science 37 (2010) 2081e2092
and secondary distributor of Mulargia millstones in north Africa.
The fact that Mulargia millstones (like those from Orvieto) were
exported to parts of the Mediterranean where local lavas were
present and used is an indication of their good reputation (Fig. 3b).
2.6. Hawaiites and mugearites from Mongibello e Etna (and basalts
from Pantelleria)
As recognized by Williams-Thorpe (1988), Etnean hawaiites,
mugearites and, to very minor extent, basalts were widely employed
in the production of millstones in antiquity (locally begun in the
Bronze Age; Ferla et al., 1984). We can assume e as also revealed by
the finds of grinding tools dating back to the sixth century BC both in
the Apulia region (Lorenzoni et al., 2000a,b) and Istria and ItalianSlovenian Karst (Antonelli et al., 2004) e that their trade was already
well organized during protohistory. Old and recent studies
(Williams-Thorpe, 1988; Volterra and Hancock, 1994; Lorenzoni
et al., 1996; Buffone et al., 2000, 2003; Renzulli et al., 2002a;
Antonelli et al., 2005) documented the presence of Roman millstones made of these rocks not only within Sicily but also in centralsouthern Italy (Marche, Apulia and Campania regions), Spain
(Ampurias), Tunisia (i.e., Carthage, Thuburbo Maius, Utica, El
Maklouba, Thapsus), Tripolitania and Cyrenaica (Lybia). WilliamsThorpe (1988) noted the presence in North Africa (Tunisia) of artefacts both from Mt. Etna and the Sicilian Na-alkaline volcanic islands
traditionally considered as the historical sources of basaltic s.l. millstones (i.e. Pantelleria and, to a very minor extent, Ustica) but
unfortunately the paper does not present the complete chemical
data for all of the numerous millstones considered. Antonelli et al.
(2005) clearly identified Roman millstones manufactured with
Pantellerian basalt and Etnean mugearite in the provinces of Tripolitania (at Leptis Magna) and Cyrenaica (at Cyrene) which are among
the southernmost production areas of grain in the Roman Empire.
Sicily and the adjacent small islands provided both obvious stopover sites and important millstone sources on the traditional northsouth axis of the wheat trade (as mentioned by Strabo, VI.2.3: Etna).
All the above-mentioned research papers indicate the Mongibello
stratovolcano lava flows as the source of the Etnean raw material
exploited by Romans (Fig. 2). More specifically, it was ascertained
that the most widely worked rocks were mugearites and hawaiites
belonging to the Mongibello Recente activity (Cristofolini et al., 1991),
dating from 14 ka to the present (Peccerillo, 2005). Williams-Thorpe
(1988) first and Renzulli et al. (2002a) later suggested that the Fratelli
Pii quarry (on the outskirts of Catania and dating from 693 BC) was
another of the Roman sites regularly exploited to work hawaiitic
millstones. Following Buffone et al. (2003), who detected four
Etnean rotary-millstones at Pompeii, an additional possible Roman
site for the production of mugearitic millstones may be found within
the outcropping area of the Pizzi Deneri formation (Older Mongibello; Coltelli et al., 1994).
3. Useful petrographic and geochemical markers for
archaeometric purposes
Petrographic and geochemical features here summarised have
been generally taken from the recent literature considering at least
six samples (more often ten or tens) for each kind of lava. To avoid
analytical bias, most of chemical data considered refer to the XRF
analytical method for major and trace elements. In the case of the
leucite-bearing lavas from the Orvieto region we used the current
database which was produced by ICP-OES-MS methods (Antonelli
et al., 2001). Anyway, a comparison between these data and those
produced through XRF on few samples of the same rock-type
(Buffone et al., 2000) proved a satisfactory analytical compatibility
for the most discriminant elements.
3.1. Euganean trachytes from the Venetian Volcanic
Province e They are mildly vesicular and of a colour that varies
through the different shades of grey
According to the usual TAS classification diagram (Fig. 5a) these
rocks are principally transitional trachytes, seldom rhyolites or
trachyandesites. Capedri et al. (2000) outlined mineralogicalpetrographic, and chemical parameters characterising the trachytes
of the most important historical quarries of the district. From
a compositional and textural point of view Euganean trachytes are
always porphyritic lavas (PI mainly from 20vol.% to 40vol.%),
frequently not seriate and with glomerophyre aggregates. Anorthoclase
(Na-sanidine) > plagioclase > biotite Mg-kaersutitic
amphibole clinopyroxene are the main phases as phenocrysts
(Fig. 4d); titano-magnetite, apatite and zircon are ubiquitous
accessory minerals, whereas titanite only crystallises in a few
trachytes (Monselice, Monte Merlo, Monte Trevisan). Phenocrysts
of allotriomorphic to euhedral anorthoclase, with crystals varying
from 2 to 10 mm in size, frequently show evidence of internal
melting (spongy texture) and very thin rims of new anorthoclase
overgrowths. Euhedral to subhedral plagioclase phenocrysts are
often zoned and may also be rimmed by anorthoclase or Na-sanidine. Biotite and, when it occurs (Monselice, Monte Merlo and not
many others), amphibole are frequently oxidised and embayed-reabsorbed. Fabrics are characterised by a holo-microcrystalline
groundmass containing feldspar microlites (mainly of anorthoclase) which sometimes show sub-parallel orientation due to
magmatic flow (pilotaxitic/trachytic textures; e.g. lavas from the
Monselice and Monte Oliveto areas) as well as no fluidal orientation
(felty texture; e.g. trachytes from Monte Cero, Monte Altore, Monte
Rosso, Monte Merlo, Monte Lispida and many other areas; Capedri
et al., 2000); small amounts of interstitial quartz and, occasionally,
minute interstitial brownish glass may also be present in the
groundmass. It is very common to see grey-black inclusions with
porphyric/granitoid/very weakly schistous fabric normally referring to trachyandesitic, gabbroic and cornubianitic composition,
respectively (Lazzarini et al., 2008 and reference therein), that
contain a larger amount of biotite, amphibole, pyroxene and
magnetite than ordinary trachyte, and sometimes small amounts of
calcite; more rare are white-gray xenoliths of alkaline-rhyolites or
granitoid rocks.
With regard to the chemical composition, general common
features are K2O/Na2O ratio around 1, the absence of Nb-Ta negative
anomalies and the presence of Q and Hy in the CIPW norm (Milani
et al., 1999). As described by Capedri et al. (2000), trachytes of
individual quarrying areas are chemically quite homogeneous, but
there is a rather wide chemical variability among the different sites,
which allows a good differentiation within the main Roman sources. The authors consider TiO2, Zr, Th, Nb, Y, V, Rb, Sr and Pb
particularly useful for discriminating and propose some valuable
binary plots able to reduce all the main quarried trachytes to five
fields (Th vs Sr; Fig. 8a) and to separate the stone varieties
belonging to the fourth and fifth field groups (i.e., TiO2, Rb and Zr vs
K2O; Y vs Nb and V; TiO2 vs Th and Zr; Fig. 8b).
3.2. Leucite phonolite from Orvieto
From a petrographic point of view these rocks can be described
as grey to light-grey vesicular (vesicules around 10e15vol.%) leucitebearing lavas, characterised by large euhedral leucite phenocrysts
(mainly 8e18 mm in size) which show complex zoning and
frequent inclusions of pyroxene plagioclase opaque minerals.
Among the most common micro- and phenocrysts (Porphyritic
Index 25e30vol.%) are also green clinopyroxene (Fig. 4a), sanidine,
plagioclase (as strongly zoned single crystals, or as aggregates), at
F. Antonelli, L. Lazzarini / Journal of Archaeological Science 37 (2010) 2081e2092
2087
Fig. 4. Photomicrograph of a thin section of a sample of a: (A) leucite phonolite from the Orvieto Roman quarry: leucite (lct) and clinopyroxene (cpx) phenocrysts in a microcrystalline-pilotassitic groundmass (gdm) which is mainly feldspathic leucite Mg-Fe minerals; (B) leucite phonolite used for the catillus D3 found in Djemila; (C) Etnean
mugearite showing plagioclase, clinopyroxene olivine (ol) phenocrysts in a microcrystalline-intergranular groundmass; (D) Euganean trachyte from the Roman site of Monte
Rosso: anorthose (anr), plagioclase (pl), biotite (bt) and clinopyroxene (cpx) phenocrysts in a microcrystalline groundmass; (E) Vesuvian basaltic trachyandesite from the Castello di
Cisterna area, showing augite (cpx), plagioclase olivine and leucite phenocrysts and aggregates embedded in a microcrystalline groundmass mainly made of feldspar, pyroxene
and FeeTi oxides; (F) tephrite from the Vulture Volcano: haüyne (hyn) and clinopyroxene phenocrysts in a fine-grained groundmass. Crossed polarized light; long side of the
pictures is 2.5 mm except for (F) for which is 5 mm.
times rimmed by sanidine, and FeeTi oxides. The microcrystalline
pilotassitic to intergranular groundmass consists of sanidine,
leucite and plagioclase microlites with subordinate clinopyroxene
and ore minerals (Fig. 4a). As regards geochemistry, these lavas are
evolved members, strongly undersaturated in silica, belonging to
the Roman-type high potassium series (HKS; Peccerillo, 2005;
average K2O/Na2O > 2.5) of the Roman Magmatic Province
(Appleton, 1972). According to the modal mineralogy and Total
Alkali-Silica classification diagram (TAS; Le Maitre et al., 1989), they
are essentially phonolites (Fig. 5a). More specifically, they show
appreciable enrichment in light rare earths (LREE), La, Sr, Th and,
Ba, together with Nb and Ti negative anomalies, which are all
typical features of the subduction-related Quaternary potassic
rocks from the north-west sector of the Roman Volcanic Province
(Serri, 1990). As verified first by Antonelli et al. (2000, 2001), in the
case of the rocks from the Orvieto quarries, their highest abundance
of La (172e228 ppm), Sr (1823e2167 ppm), Th (136e178 ppm) and
Ba (1957e2340 ppm) are very useful chemical fingerprints for
differentiating these leucite phonolites from the other similar rocks
outcropping within the Roman Volcanic Province. La, Th, Sr versus
Ba binary diagrams proved to be the most efficient for this purpose
(Antonelli et al., 2000, 2001; Renzulli et al., 2002a; Santi et al.,
2004; Fig. 6a). The possible overlapping of the Vulture and
Orvieto fields in the diagram Ba vs Sr can be easily resolved through
the petrography (discriminant presence of haüyne in the lavas from
Vulture; infra).
Similar petrographic (Fig. 4b) and geochemical (Figs. 5 and 6a)
features have been found for two catillus (#D ¼ h: 42 cm, internal
Ø: 25 cm; #D3 ¼ h: 37 cm, internal Ø: 24 cm) and one meta
(#D4 ¼ h: 30 cm, maximum Ø: 25 cm) discovered in the ancient
Cuicul (Algeria). Results of the petrochemical study conducted on
them are summarised in Figs. 4e6 and Table 1.
3.3. Somma-Vesuvius leucite basaltic trachyandesites from Castello
di Cisterna
They are highly porphyritic lavas (PI ca 50e65vol.%); augitic
euhedral clinopyroxene (mainly 3 mm in size; Ømax 5 mm),
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F. Antonelli, L. Lazzarini / Journal of Archaeological Science 37 (2010) 2081e2092
the phonolitic tephrites. These rocks, as always for the potassic
series (KS; Peccerillo, 2005) of the Roman Magmatic Province, are
characterised by K2O/Na2O ratios varying from 1.5 to 2.5
(often < 1.8; Joron et al., 1987), absence of Ba and P negative
anomalies (Serri, 1990), La 43e48 ppm, Sr 673e696 ppm and Ba
1449e1502 ppm (Buffone et al., 2000, 2003). Their mineralogical
and chemical compositions suggest to classify they as shoshonites
and allow these leucite-bearing lavas to be readily differentiated
from the others outcropping within the Roman Volcanic Province
(Fig. 6a).
3.4. Tephrites-foidites from Vulture (Potenza, Basilicata)
Fig. 5. (a) The alkali-silica classification (TAS) of both the six Italian volcanic millstone
source rocks object of this paper and the analyzed leucite-bearing volcanic millstones
from Cuicul (Algeria: full triangles). Diagram (after Le Maitre et al., 1989) includes the
subdivision of volcanic rocks into alkaline and subalkaline. The boundaries are as
follows: ¼ Kuno, 1966; < ¼ Irvine and Baragar, 1971. Abbreviations: H: hawaiites; M:
mugearites; TA: trachyandesites; T: trachytes; PB: picro-basalts; B: basalts; BA: basaltic
andesites; BT: basaltic trachyandesites; A: andesites; D: dacites; Te-Bs: tephrites and
basanites; PhTe: phono-tephrites; TePh: tephri-phonolites; Ph: phonolites; F: foidites;
R: rhyolites. (b) Na2O vs. K2O variation diagram for both the principal Italian volcanic
raw material sources and the analyzed leucite-bearing volcanic millstones from Cuicul
(full triangles). Fields marked with gray broken lines refer to the three main leucitebearing lava sources (Orvieto, Vesuvius, Vulture). Data referring to basic lavas from
Pantelleria, Ustica and Hyblean Plateau are plotted for comparison with Etnean lavas.
Separation among HK, K and Na series classically adopted for alkaline basic rocks (after
Middlemost, 1975), is plotted too (grey dashed lines) to show the Na-affinity of all the
Sicialian lavas. Data for comparison are from: Antonelli et al., 2001 and Buffone et al.,
2000 (open triangles: leucite-bearing lavas from the Roman quarries of Orvieto, Vulsini
Volcanic Discrict); Cristofolini et al., 1991 (circles: hawaiites and mugearites from the
Mt. Etna, Mongibello Recente); Buffone et al., 2000 (squares: leucite basaltic trachyandesites from Castello di Cisterna, Somma-Vesuvius); De Fino et al., 1986;
Williams-Thorpe, 1988 and Beccaluva et al., 2002 (crosses: tephrites-foidites from
Vulture Volcano; Capedri et al., 2000 (open diamonds: trachytic lavas from Euganean
Hills); Williams-Thorpe, 1988 and Williams-Thorpe and Thorpe, 1989 (asterisks:
rhyolitic ignimbrite from Mulargia); Civetta et al., 1984, 1998 (rotated crosses: alkaline
and transitional basalts from the island of Pantelleria); Trua et al., 1998 (full gray
asterisks: alkaline basalts from the Hyblean Plateau); Trua et al., 2003 (crossed
squares: basic lavas of Ustica). Separation among HK, K and Na series classically
adopted for alkaline basic rocks (after Middlemost, 1975), is plotted too (grey dashed
lines) to show the Na-affinity of the Sicialian lavas.
idiomorphic leucite (Ømax 4e5 mm), labradoritic-bytownitic
plagioclase (Ømax 2 mm) and olivine (Ømax 1.5 mm) are the most
abundant phenocrysts respectively (Fig. 4e); occasionally rare
sanidine may also be present. Pyroxene, leucite and plagioclase
may each form polycrystalline aggregates. The microcrystalline
groundmass consists (in decreasing order of abundance) of feldspar, pyroxene, leucite, FeeTi oxides, phlogopite and apatite.
In the TAS diagram (Le Maitre et al., 1989; Fig. 5a) they fall
essentially in the basaltic trachyandesites field, seldom in that of
Unlike the volcanic complexes aligned from Vulsini to Vesuvius
along the Tyrrhenian margin of Italy, Mount Vulture is located near
the easternmost border of the Appennine compressive front. This
peculiar structural setting is accompanied by a unique composition
of magmas and derived alkaline rocks, which are characterised by
both K and Na enrichment (Beccaluva et al., 2002) as well as by
common presence of haüyne in all the volcanic products (De Fino
et al., 1986; Beccaluva et al., 2002; Peccerillo, 2005).
Tephrite-foidite vesicular lavas (vesicles ca 35vol%) used for
millstones show evident porphiritic texture (PI ca 30e35vol%) and
are composed of phenocrysts mainly of green pyroxene and
haüyne >> leucite and nepheline biotite and apatite (Fig. 4f).
They are embedded in a very fine-grained groundmass in which
opaque minerals, plagioclase, pyroxene, feldspathoids and occasionally K-fedspar may be recognizable. Pyroxene phenocrysts,
generally abundant and zoned, have fairly irregular form and
inclusions of haüyne, opaques and nepheline. Those of haüyne are
common or abundant and usually appear smaller and more
rounded than pyroxene. Their colour is typically blue at the rim.
Finally nepheline, leucite and biotite (which may be altered)
phenocrysts are commonly small in size. Using the TAS diagram
(Fig. 5a) these lavas fall in the tephrite, tephrifonolite and foidite
fields in agreement with the petrographic classification (De Fino
et al., 1986; Caggianelli et al., 1990; Beccaluva et al., 2002;
De Astis et al., 2006). Geochemistry reveals that they belong to
the potassic alkaline series (De Fino et al., 1982, 1986) of the Roman
Magmatic Province, with K2O/Na2O variable, but frequently high
(always > 1) although haüyne is the dominant feldspathoid
(Lorenzoni et al., 2000a). In these basic lavas the K/Na ratio is
similar to those of KS basic magmas (Fig. 5b), but the enrichment of
most incompatible elements and the degree of silica undersaturation are close to those of HKS magmas (De Fino et al., 1986).
CaO and TiO2 vol% are mainly 8.1e12.4 and 0.8e1.4, respectively,
while, with regard to trace elements, the Zr values are generally
between 305 and 570 ppm, V varies roughly from 180 to 270 ppm,
Sr approximately from1600 to 2850 ppm, Rb from 70 to 170 ppm,
Ba from 1700 to 2800 ppm and Y roughly from 40 to 60 ppm
(De Fino et al., 1986; Lorenzoni et al., 2000a; Beccaluva et al., 2002;
De Astis et al., 2006). In the Mediterranean basin as a whole these
mineralogical and geochemical compositions (cfr. Figs. 6a and 7)
are peculiar just to Mt. Vulture, the only volcano to have such
abundant haüyne in the emitted products (among all the volcanoes
of the Roman Magmatic Province negligible amounts of haüyne are
present only in the Roccamonfina lavas) (Lorenzoni et al., 2000a).
3.5. Rhyolitic ignimbrite from Mulargia (Sardinia)
This ignimbrite has a distinctive red colour with paler fiamme
and contains many sharp edged vesicles (usually about 1e3 mm in
size), very often lined with a typical green mineral, supposed to be
celadonite (Williams-Thorpe and Thorpe, 1989) probably mixed
with some kind of zeolite. In thin-section it exhibits a brown-red
F. Antonelli, L. Lazzarini / Journal of Archaeological Science 37 (2010) 2081e2092
2089
Fig. 6. (a) Sr vs. Ba discrimination diagram for the most important basic to intermediate Italian lavas; data are compared with those obtained for the leucite-bearing volcanic
millstones discovered in Cuicul (full triangles). Grey fields refer to Vulsini Volcanic District. (b) Sr vs. TiO2 discrimination diagram for the most exploited Italian basic lavas. Data for
comparisons are from: Villari, 1974; Civetta et al., 1984; Williams-Thorpe, 1988; Esperanca and Crisi, 1995; Civetta et al., 1998 (rotated crosses: alkaline and transitional basalts from
the island of Pantelleria); Romano and Villari, 1973; Trua et al., 1998 (full gray asterisks: alkaline basalts from the Hyblean Plateau); Cinque et al., 1988; Williams-Thorpe, 1988; Trua
et al., 2003 (crossed squares: basic lavas of Ustica); Antonelli et al., 2000, 2001 (open triangles: leucite-bearing lavas from the Roman quarries of Orvieto, Vulsini Volcanic Discrict);
Conticelli et al., 1997 (long dashes: leucite-bearing lavas from the Sabatini Volcanic Complex); Antonelli et al., 2001 (short dashes: leucite-bearing lavas from the Vico Volcano); De
Fino et al., 1986 and Beccaluva et al., 2002 (crosses: tephrites-foidites from Vulture Volcano); Buffone et al., 2000 (basaltic trachyandesites from Castello di Cisterna, SommaVesuvius; open squares: quarry samples; full squares: millstones); Cristofolini et al., 1991 (open circles: hawaiites and mugearites from Mt. Etna, Mongibello Recente); Tanguy et al.,
1997 (full circles: tholeiitic basalts from Mt. Etna Volcano).
glassy (often devitrified glass) groundmass, showing traces of flow
structure (Peacock, 1980), embedding very rare phenocrysts of
quartz and andesine feldspar biotite opx. This rock outcrops in
the north-west of the Sardinia and belongs to the relatively high K
calc-alkaline dacite-rhyolite lava series erupted during the
OligoceneeMiocene (30e13 ka) subduction of lithospheric plate in
the SardinianeCorsican microplate environment, so it shows
chemical characteristics common to island-arc related rocks
(Dostal et al., 1982; Peccerillo, 2005). Following data reported by
Williams-Thorpe (1988) and Williams-Thorpe and Thorpe (1989)
the Mulargia ignimbrite exhibits low concentrations of Cr
(ca 2e20 ppm); Rb ca 140e165 ppm; Sr ca 150e190 ppm, Y ca
30e53 ppm; V ca 20e43 ppm; Zr ca 200e230 ppm, TiO2 around
0.60%, SiO2 ca 67e69; Al2O3 ca 14.9e16%; K2O/Na2O ratio roughly 1
(frequently slightly < 1) and K2O þ Na2O 8%. Obviously, to prove
univocally a provenance from Mulargia, petrochemical analyses
should be always necessary for a scientific validation of the origin of
this high-silica rock (Figs. 6a and 7). Unfortunately, due to its
general macroscopic aspect, supposed to be sufficiently distinctive
to identify it in hand specimens directly with the naked eye by most
of the archaeologists, archaeometric analyses concerning this kind
of volcanic millstones are very rare (few analyzed samples are
reported just in Williams-Thorpe, 1988 and Williams-Thorpe and
Thorpe, 1989).
3.6. Etnean hawaiites and mugearites from Mongibello
(and basalts from Pantelleria)
Mugearites and hawaiites are generally grey to dark-grey
slightly vesicular (vesicles 10%) seriate lavas often characterised
by evident porphyritic texture (PI: 20e60 vol.% ca for mugearites;
30e50 vol.% ca for hawaiites). Mugearites have microcrystallineintergranular groundmass made up of plagioclase, opaque
minerals and less abundant pale-green or colourless clinopyroxene. Phenocrysts and microphenocrysts are represented by plagioclase >> clinopyroxene > olivine > FeeTi oxides (Fig. 4c).
Euhedral (labradoritic)-bytownitic plagioclases are the largest
ones (4e5 mm in size) and often feature spongy texture, deep
embayments, glass and opaque inclusions. Augitic pale-green
pyroxene is normally small in size (mainly 0.5 mm, sometimes up
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F. Antonelli, L. Lazzarini / Journal of Archaeological Science 37 (2010) 2081e2092
Fig. 8. (a): Sr vs.Th diagram for the discrimination of quarried sites of the trachytes in
the Euganean Hills (fields and data from Capedri et al., 2000). Field 1: Monselice; Field
2: Mt. Trevisan; Field 3: Mt. Altore, Mt. Pendice; Field 4:Mt. Oliveto, Mt. Bello, Mt. Cero,
Mt. Lonzina, Mt. Lozzo, Mt. Merlo, Mt. Murale, Mt. Rosso; Field 5: Mt. Alto, Mt. Grande,
Mt. Lispida, Mt. Oliveto2, Mt. Rusta, Mt. S.Daniele. (b): TiO2 vs. Zr diagram for the
discrimination of the Euganean trachytes falling in field 4 of Fig. 8a (fields and data
from Capedri et al., 2000). Gray filled circles refer to three Roman mills from Antonelli
et al., 2004 and one Roman millstone from Aquileia (unpublished data).
Fig. 7. Discrimination among the six main Italian millstone source rocks considered in
this paper using Zr and V (after Williams-Thorpe, 1988, modified). For comparison with
Etnean lavas, data referring to other basic Sicilian rocks are plotted too. The gray
broken line separates the acid from the basic-to-intermediate rocks. Data are from:
Williams-Thorpe, 1988; Trua et al., 2003; Peccerillo, 2005, for Pantelleria, Hyblean
Plateau and Ustica; Antonelli et al., 2001 and Buffone et al., 2000, for Orvieto region;
Capedri et al., 2000, for Euganean Hills; Cristofolini et al., 1991, for Etnean “Mongibello
recente” lavas; Williams-Thorpe, 1988 and Beccaluva et al., 2002, for Mt. Vulture;
Williams-Thorpe, 1988 and Williams-Thorpe and Thorpe, 1989, for Mulargia. Symbols
are as in Figs. 5 and 6. Full triangles are the analyzed millstones from Cuicul. Small pale
grey circles refer to Roman millstones analyzed by scholars cited in the text and to one
unpublished trachytic millstone from Aquileia.
to 3.5 mm), whereas olivine phenocrysts are smaller (mainly 0.5 mm in size) and show a rounded habit.
Hawaiitic lavas have microcrystalline-intergranular groundmass
composed of plagioclase, clinopyroxene, olivine and FeeTi oxides.
They include pheno- and microphenocrysts of euhedral sieved
plagioclase (up to 3 mm in size, with opaque and glass inclusions) >
augitic green to brownish pyroxene (up to 2 mm in size and
including oxides) sub-rounded olivine (around 1 mm in size; on
occasion in glomerophyric associations with clinopyroxene).
As concerns the geochemical characters of mugearite, hawaiites
from Mongibello Recente, they refer to original magmas related to
an extensional within-plate regime and with a weak Na-alkaline
affinity; This is shown, for example, by the Th/Nb (see, e.g., Fig. 8 of
Beccaluva et al., 1991) and K2O/Na2O ratios (¼0.5; Peccerillo, 2005).
In particular, useful fingerprints are represented by TiO2 < 2 wt. %,
high Sr values (>1000 ppm) and Ba (>700 ppm) (Cristofolini and
Romano, 1982; Cristofolini et al., 1991; Peccerillo, 2005). Furthermore, Sr vs Ba (Fig. 6a), Nd, Sr vs TiO2 (Antonelli et al., 2004, 2005;
Fig. 6b) or Zr vs V (Fig. 7; after Williams-Thorpe, 1988, modified)
diagrams can be quite valuable for discrimination between our
basic lavas and those from other Etnean areas (tholeiitic basalts),
Hyblean Plateau (alkaline and transitional basalts), Ustica (alkalibasalts, hawaiites and mugearites), and Pantelleria (alkaline and
transitional basalts); these are virtually all possible sources for
Roman volcanic millstones. In particular, as reported by WilliamsThorpe and Thorpe (1990), Pantelleria was a producer of small,
relatively simple millstones from at least the Bronze Age to the
Roman period. Basaltic lavas outcropping as far as the coast in the
northern (at San Leonardo and Mursia; Civetta et al., 1984) and
north-east parts of the island (at Le Balate; Villari, 1974; Civetta
et al., 1984) were the most probable flow sources. Specifically, the
dark-grey vesicular, olivine-basalts of San Leonardo, which are
F. Antonelli, L. Lazzarini / Journal of Archaeological Science 37 (2010) 2081e2092
characterised by a seriate porphyritic texture (PI 25e30 vol. %;
phenocrysts: labradoritic- bytownitic plagioclase > augitic clinopyroxene > olivine), microcrystalline-intergranular groundmass
(plagioclase þ clinopyroxene þ FeeTi oxides olivine), chemical
transitional/sodic affinity (K2O/Na2O ratio 0.3, TiO2 > 2 wt. % and
Sr < 550 ppm; Villari, 1974; Civetta et al., 1984, 1998), were the raw
material used to obtain some Roman millstones discovered in
North Africa, specifically in Tunisia and Libya (Peacock, 1985;
Williams-Thorpe, 1988; Antonelli et al., 2005).
As regards other possible Sicilian lava sources, the use of alkaline
and transitional basalts from Ustica and Hyblaean Plateau, as well
as of andesites from the Aeolian island of Lipari is very rare outside
the Sicilian district; very few Roman mills and grindstones made of
these lavas have been identified on the Italian mainland
(for example one possible grinding tool of Hyblean origin at
Fossombrone, Marches; Renzulli et al., 2002a) and in North Africa (a
quern made of trachybasalt from Ustica is mentioned at Carthage
by Williams-Thorpe, 1988).
4. Conclusions
The petrographic and geochemical features summarised above,
when used together (possibly integrated by critical historicalarchaeological data too) may produce reliable results concerning
the origin of the Italian raw material of the Roman volcanic
millstones. This approach enables most millstones to be attributed
to a geological source, if not ever with absolute certainty then
surely with a fully acceptable degree of reliability. For three decades
at least, the petrochemical study of millstones (and all of the
geomaterials) has made substantial contributions to archaeological
research into the reconstruction of ancient communication routes,
trade networks and cultural links in different periods. Volcanic
rocks outcrop in limited areas within the Mediterranean basin as
a whole and Italian volcanics played a primary role in the
production and trade in millstones during the Roman period. This
paper brings together the petrography and major-trace elements
geochemistry of the most exploited and widespread Italian volcanic
rocks worked as millstones during the Roman period as well as
a general evaluation of the amount and geographical extent of
the trade for millstones of each stone typology within the
Mediterranean.
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