Materials, geological sources and analyses of metal provenance

In document 9789088902444 - Wilkinson 2014 - Tying the Threads of Eurasia - eBook (Page 155-170)

Mapping Material Flows: Metals

5.2 Materials, geological sources and analyses of metal provenance

The distribution of mineral resources and their likely exploitation during the period of interest provides an obvious starting point for an examination of the flow of metals. Considerable literature and research effort have been devoted to the identification of potential raw material sources (e.g. Artioli et al. 2005; Alimov et al. 1998; Bayburtoğlu and Yıldırım 2008; Berthoud et al. 1982; Boroffka et al. 2002; Brovender 2009; Charles 1985; Craddock 1980; de Jesus 1978, 1980;

Helwing 2005; Momenzadeh and Sadighi 1989; Muhly 1973, 1985, 1993; Stöllner

et al. 2004; Stöllner 2005; Wagner, Öztunalı and Eibner 1989; Wagner and Öztunalı 2000; Wertime 1973; Yener 1986; Yener and Vandiver 1993a), extensive programmes of research involving chemical and isotopic analysis of metal objects to attempt to identify the source of their constituent materials (e.g. Agrawal 2000;

Artioli et al. 2005; Begemann et al. 2008; Begemann and Schmitt-Strecker 2009;

Berthoud et al. 1982; Chegini et al. 2000, 2004; Courcier 2007; Frame 2010;

Gale and Stos-Gale 1999; Gillis et al. 2003; Hauptmann and Weisgerber 1980;

Hauptmann, Rehren and Schmitt-Strecker 2003; Helwing 2005; Kaniuth 2006;

Vatandoust, Parzinger and Helwing 2011; Weeks 2003; Webb et al. 2006), and more synthetic reconstructions of regional patterns and the routes that such raw materials took to reach metal consumers (e.g. Potts 1994, 143-176; Kroll 2002;

Muhly 1993, 1999, 2005; Pigott 1999a; Roberts, Thornton and Pigott 2009;

Stech and Pigott 1986).

Our discussions of metal sources and their routes of movements remain necessarily partial and open to reinterpretation, however (Palmieri, Sertok and Chernykh 1993). Four main factors make the investigation of the movement of metals through comparison between geological sources and metal objects difficult, outlined clearly by Chernykh (1992). First, whilst there has been considerable investigation into ancient metal ore sources, there are many gaps in our knowledge. Modern geological research and mining activities may reveal the occurrence of regions rich in particular ores, but given the nature of mining as extractive excavation, positive evidence for ancient exploitation of particular resources in particular periods is extremely difficult to find. For example, whilst the distribution of certain metal types and objects appears to favour the Caucasus as a major exporter of copper alloys to the steppes to the north in the Early Bronze Age, there is paradoxically little or no direct evidence of mining or smelting from the region itself in this period (Chernykh 1992, 59, 276). Smaller sources may be especially difficult to identify, since the minerals may have been exhausted in the past. Added to this is the fact that geological investigations tend to be conducted on a country-by-country basis, and it is often difficult to pull the diverse data together. Secondly, the techniques of characterization of metals and ores, which might allow the identification of raw materials for given objects, are complicated by the geological indeterminacy of mineral sources (and our incomplete knowledge of them) and the effects of metallurgical processing. The transformation of ores to workable metals often results in fractionation of the impurities that would otherwise identify a particular ore source. Thirdly, metals were continually recycled in antiquity, as old, stolen or broken metals were melted down and recast into new shapes, often resulting in mixing of metals from diverse sources and obscuring any identifying signatures53. Finally, the main reasons for this recycling, metal’s high value and universal exchange functions, also have consequences for its archaeological visibility: in comparison to their likely usage and circulation, metal objects were deposited intentionally only under special circumstances, and less likely to be casually lost or thrown out than some other materials (unlike broken pottery, broken metal is re-used). The corpus of metal objects in the archaeological record is thus only a fraction of the amount that must have been circulating in antiquity, and substantially less representative than

53 It is fascinating to speculate as to the percentage of metals in circulation today that have been continuously remelted for 6000 years!

certain other materials. Despite this, very large databases of objects and analyses can yield useful results in different fields (see Section 5.4).

Whilst modern geological surveys can identify areas of high concentrations of certain minerals (or at least mineralogical zones), and hence offer general ideas about potential sources, unequivocal evidence of exploitation of particular resources at particular periods is extremely difficult to find. Since mining is an extractive process, resources mined in antiquity may have been exhausted, and therefore remain unrecognized. In Anatolia, where the Turkish MTA (the state geological and prospection service) has investigated and published detailed data on the mineralogy of the region and found evidence of ‘old workings’, it remains difficult to assign a date (cf. Wagner, Öztunalı and Eibner 1989; Wagner and Öztunalı 2000). Based on material remains it has been suggested that Classical, Byzantine and Ottoman periods witnessed substantial mineralogical exploitation, often still remembered in place-names54, but arguably this reflects a general bias in the material record as a whole. In the Caucasus and especially Central Asia, the political fragmentation of territory – one of the outcomes of the European imperialist ‘Great Game’ (Meyer and Brysac 1999) – has resulted in fragmented geological knowledge, and few cross-border syntheses. In both regions certain

‘headline’ sources are cited repeatedly in general literature: for example the Ergani copper and silver sources near Diyarbakır; the copper sources on Cyprus55; or the much cited but little investigated sources of tin in Afghanistan and Central Asia.

5.2.1 Social and ritual aspects of mining

The broadly positivist outlook of archaeometallurgical research makes it difficult for newly identified potential sources to enter the canon, and it can be difficult to make sense of the polarized accounts offered by different researchers. For example, the suggestion that tin may have been extracted in the western Taurus at Kestel (Yener and Vandiver 1993a; Yener 2000) during the Early Bronze Age has caused considerable controversy (see discussion below, Section 5.2.3).Whether or not one believes that the particular mining and metallurgical evidence from Kestel/

Göltepe proves the extraction of tin in Anatolia at this time, the very possibility should open our minds to the idea that multiple small sources might have been exploited at times (perhaps coming in and out of use), and not just the large sources of ore cited so frequently. Deposits which are economically unviable in the modern day may have been otherwise in the past. Similarly, mining is dependent on particular (and therefore culturally-bound) knowledge about earth-based resources, as conceptualized and integrated within the various social spheres through which the materials flowed. Ancient and modern commercial exchange of minerals relied, and still relies upon today, pre-defined and sometimes conservative distribution structures. In order to procure metal objects, one has to go to a metal specialist (the smith), who in turn will procure regularly from a set of sources known to this specialist. In a commercial setting the relationship may sometimes be impersonal and choice of source dependent on market prices, but often long-term relationships between dealers (which in small-scale communities, may

54 For example, in Turkish place names: gümüş – silver, maden – mine or mineral, altın – gold, bakır – copper, kalay – tin.

55 The name of the island providing (or being provided by) the word for copper in ancient Latin.

intersect with kinship, friendship or other obligation networks), or requirements for ritual/symbolic qualities of the material may play a more important role than mere price in the selection of material.

By way of illsitration, it is very likely that colour and visual properties (e.g.

lustre) played an important role in ancient prospection, as they did in the production of finished objects. Given the various ‘symbolic’ values that colours may take on under different situations56, it is interesting to consider whether choices of ores and production of coloured artefacts were not just functional or abstractly ‘aesthetic’ but also ‘ritual-symbolic’ (cf. Killick 2009). The earliest usage of copper objects in the form of coloured beads (Muhly 1989), contextualizes copper as merely one ‘precious’ stone amongst many (such as carnelian, lapis, quartz, obsidian, cf. Section 4.3), albeit each must have its own characteristics and associations (A. Sherratt 1976). Technical advances along the road to metallurgy and metalworking must have had cultural-aesthetic roots. For example, Pigott (1999a) has argued that the earliest evidence for copper working in Iran may relate to the ‘attractive’ colour and naturally malleable properties of native copper, and that the subsequent development of smelting and arsenic-bronzes may have been an accidental discovery due to the colour similarity of certain copper-arsenide ores (algodonite and domeykite), which are indistinguishable from native copper.

The way in which certain ores were recovered may also have differed in the past. Whilst we tend to picture mining as the direct extraction of rock from the ground, ‘panning’ may have been a more common technique to collect many different types of metals and precious stones. Many minerals are ‘worked out’ of rock-based deposits by the action of water (rain, rivers or glaciers), and it is not difficult to imagine the symbolic and mythological associations that might be created through this association as water feeds both biological and socio-economic life: our modern divisions between organic and inorganic life may be anachronistic to ancient world-views.

If the above paragraphs appear to over-emphasize the ritual and the symbolic, then it is as a corrective against the most common narratives about ancient raw metal sources which tend to situate activities of ore procurement and metallurgy within a field of de-contextualized or de-ritualized technology (cf. similar critique in Budd and Taylor 1995; Rowlands and Warnier 1993). In this orthodox perspective, issues of functional advantage and Lamarckian evolutionary progression come to the fore, at the expense of cultural context and the unpredictable messiness of the material record. The use of certain alloys of copper (especially tin-bronze) or iron have been seen as a line along a ‘normal’ trajectory of technical progress. Though there are definite patterns of technology, this approach is barren in that ultimately it reduces differences of adoption of certain technologies to how ‘advanced’ a particular culture is, rather than attempting to analyse the social motive behind the invention, adoption or rejection of technical skills and knowledge (cf.

Rahmstorf 2011). In response, the technico-positivist perspective can argue that a cultural approach sometimes ignores the specificities of technical process and real ‘advantages’ of some materials and techniques over others. Integrating the technical and symbolic aspects of metallurgy thus remains difficult, but we must

56 As illustrated by ‘imperial’ purple of Rome, or the Russian linguistic association between the word for red, красный, and beauty, hence Red Square is, in fact, the ‘beautiful’ square.

Figure 5.1. Sources of copper ore, including Ergani, Veshnoveh, Omani, Cypriot and Rajasthani regions. See Appendix D.1.2 for key to numbers.

constantly keep them both in mind if we are to have any chance of accurately reconstructing and explaining long-term changes in the flow of metals.

Whilst textual records from Mesopotamia do sometimes provide hints as to the dominant sources in the third and second millennia (Muhly 1973; Moorey 1994, 245-246), more often it is the combination of modern geological knowledge, a very sparse scatter of archaeological clues, and an impressionistic sense of the metallurgical analyses of objects and sources which must be relied upon to hint at the complex dynamics of source exploitation (cf. Potts 1994, 145-153; Sherratt 2007).

5.2.2 Sources of copper

Copper is perhaps the most important metal for the study of early metallurgy, because of its widespread use for all types of objects starting from the Chalcolithic period onwards. Modern geological reports suggest that potential sources of copper are and were widely distributed across the Old World (Wagner and Öztunalı 2000, 31), but the actual ore forms are diverse (e.g. native copper, malachite, azurite and cuprite), and not all ores may have been recognisable to ancient metallurgists at particular times. Copper ores, though widespread, are by no means evenly spread.

A summary map of the distribution of known copper-bearing regions, based on a synthesis of the current archaeological literature on the topic, shows this uneven distribution (Figure 5.1). Certain regions include copper ores with significant impurities of other metals, such as antimony, arsenic, nickel and lead; the impurities were sometimes part of the ore’s attraction, even when the additional metal was not known as a separate material in antiquity.

In Anatolia and Transcaucasia, a number of attempts have been made to identify copper sources which were exploited in the prehistoric era by projection back from modern data (e.g. see maps in Korfmann 1982, 136-137; Yakar 1985;

de Jesus 1978). More systematic and extensive surveys (Wagner and Öztunalı 2000; Palmieri, Sertok and Chernykh 1993), which have attempted to look directly for archaeological evidence, often show large-scale Roman, Byzantine and Ottoman exploitation in many areas, but found it harder to confirm prehistoric exploitation categorically. Hence, while there are known deposits of copper from which it seems highly probable that most ancient copper came (e.g. the Ergani sources in eastern Anatolia), it is also possible that smaller deposits outside these regions were known and used periodically. The main deposits include those in the West Anatolian highlands, along the eastern Black Sea, around the ‘Hittite’

highlands along the Kızılırmak river, in the hills between Malatya and Diyarbakır (especially Ergani) and in areas of modern Georgia, Armenia and Azerbaijan.

Problematically, however, direct evidence for copper ore exploitation is rather difficult to find, especially before the Late Bronze Age (Palmieri, Sertok and Chernykh 1993; Chernykh 1992, 276). The Ergani deposits show little positive evidence of exploitation, for example, but the extent of subsequent mining means that any evidence could have been destroyed, so this dearth is not particularly surprising.

Intermediate to our two main regions of interest, the Iranian Plateau contains a large number of copper sources of varying qualities and quantities. The most oft-discussed sources are those of Anarak (Talmessi/Meskani) and Veshnoveh in central Iran (Pigott 1999a; Stöllner et al. 2004; Stöllner 2005). Partly because of the extensive evidence for early Chalcolithic metallurgy in these regions and

partly because the arsenic content of some of the deposits accords with the dominant composition of copper-alloys in the Early Bronze Age corpus, many have considered these regions to have formed one of the prime sources for early Mesopotamian copper-working (see Stech and Pigott 1986; Moorey 1994, 247; cf.

recently Matthews and Fazeli 2004). Again direct datable evidence of exploitation is often elusive, however. A ceramic vessel of Sialk IV type at ‘Chale Gahr’ has been taken as suggestive evidence of exploitation in the Veshnoveh region datable to the early 4th millennium, for example (Pigott 1999a, 78; Holzer and Momenzadeh 1971, 7), but this is only a single vessel. A more promising confirmation of the region’s metal extracting importance comes from the nearby metalworking site of Arisman (Chegini et al. 2000, 2004; Pernicka 2004; Helwing 2005; Vatandoust, Parzinger and Helwing 2011). There are numerous other large copper sources

Figure 5.2. Archaeotopogram

‘type A2’ showing relative distance from copper ore sources around Eastern Anatolia. Darker colour indicates zones which are relatively closer to copper sources.

Figure 5.3. Archaeotopogram

‘type A2’ showing relative distance from copper ore sources around western Central Asia. Darker colour indicates zones which are relatively closer to copper sources.

across the plateau, and in neighbouring regions of Afghanistan, highlighted by Wertime (Wertime 1973), Berthoud (Berthoud et al. 1980, 1982; Cleuziou and Berthoud 1982) and Weisgerber (Weisgerber 1990; Weisgerber et al. 1990). As with Anatolia, it is difficult to assess the extent to which different sources played a part, and indeed how comprehensive our knowledge of the material sources is in the first place57.

Whilst recent work in Iran has considerably updated our knowledge of the metallurgy of certain areas, the most extensive investigations into Afghan sources of ancient copper, namely the French expeditions of Berthoud and team (see Berthoud et al. 1982), are now 30 years old. In south-western Central Asia, to the north-east of the Iranian plateau, the landscape is poor in minerals. In the traditionally identified heartland of Namazga cultures, for example, particularly in the areas close to the Kopet Dag, very few copper sources have been recorded on either the Iranian or Turkmen side of the borders. The copper from metal objects found in this region must have come from Iran or Afghanistan, or further to the north-east, in Bactria, the Zerafshan or Ferghana. These regions, fragmented by the modern states Uzbekistan, Tajikistan, Kyrgyzstan, northern Afghanistan, Kazakhstan and the Chinese region of Xinjiang, do contain a wide variety of mineral sources including copper ores (Chernykh 1992, 6, 179; see also Rubinstein and Barsky 2002 for a summary of mineral resources in the former the USSR republics).

Some additional more distant regions bearing copper should be mentioned with regards to 3rd and 2nd millennium copper circulation, namely: Egypt, the Levant, Cyprus and Oman (Moorey 1994, 245-248), and also the sources of south Asia.

Investigations in Oman appear to have confirmed the importance of this region for the early extraction of copper on a large scale for Mesopotamia (Potts 1994, 149-15; Weeks 2003), and support the identification of the Persian Gulf region with ‘Magan’ of Mesopotamian texts. The Levantine and Cypriot sources may not have contributed to eastern Anatolian and western Central Asian consumers during the 3rd millennium (Muhly, Maddin and Karageorghis 1982), but it seems likely that they were supplying to local and various eastern Mediterranean communities. In the Levant, copper sources around Feinan and Wadi Arabah may have been important (Moorey 1994, 247; Levy et al. 2002), both locally and

‘internationally’. Sources of copper in Egypt (for example in the Sinai and Eastern deserts) may also have supplied Egyptian or more distant consumers. The sources of copper used by the peoples of the Indus civilization and their neighbours in the Indian subcontinent remain unclear – there are extensive deposits in Afghanistan, as has already been mentioned, but also to the east in Rajasthan. These could have been major sources, though the evidence remains moot (Hoffman and Miller 2009; Agrawal and Seshadri 1998; Agrawal 2000; Kenoyer and Miller 1999).

Omani sources may offer a more likely alternative source (Weeks 2003). Copper may have circulated in the form of standardized ingots by the mid 3rd millennium – documented in the eastern Mediterranean, for example, by the ‘Levantine’ ingot from Poros, Crete (Doonan, Day and Dimopoulou-Rethemiotaki 2007, 105-106, fig. 6.2). It seems likely then that ingots (perhaps of different types) were also circulating elsewhere, but whether it was on the bulk scale hinted at for the late

57 This is partly a result of the fragile political situation in the region, but there also has been a paradigmatic shift away from certain types of mineral investigations in archaeology generally, as the scientific techniques of provenance analysis have proven less conclusive than initially hoped (see comments in S. Sherratt 2007).

Figure 5.4. Sources of tin, including Deh Hosein, Kestel and Karnab regions. See Appendix D.1.2 for key to numbers.

14th century BC by the ingot-laden wreck at Uluburun (Pulak 1998; Sherratt 2000) is unclear.

The relative accessibility of copper sources to the surrounding regions is shown by the archaeotopograms in Figures 5.2 and 5.3. It is clear that highland regions are (unsurprisingly) disproportionately better resourced in copper than the lowland plains where urban settlements grew exponentially from the 4th millennium onwards. The overall pattern in eastern Anatolia illustrates the relative ‘closeness’

of Anatolian sources to southern Mesopotamia compared to, say Levantine or Iranian sources. This may explain the faster integration of Assyria into the Uruk cultural sphere since contacts were relatively ‘cheaper’ than those to the west

of Anatolian sources to southern Mesopotamia compared to, say Levantine or Iranian sources. This may explain the faster integration of Assyria into the Uruk cultural sphere since contacts were relatively ‘cheaper’ than those to the west

In document 9789088902444 - Wilkinson 2014 - Tying the Threads of Eurasia - eBook (Page 155-170)