AN EARLY BRONZE AGE TIN PRODUCTION SITE AT GÖLTEPE, TURKEY
By K. Aslihan Yener, Assistant Professor,
The Oriental Institute and the Department of Near Eastern Languages and Civilizations
The University of Chicago
(This article originally appeared in The Oriental Institute News and Notes, No. 140, 1994, and is made available electronically with the permission of the editor.)
The 1993 season was the third year of excavations at the Early Bronze Age workshop/habitation site of Göltepe, with its associated tin mine, Kestel, located in the central Taurus Mountains of Turkey. These sites were discovered during ten years of archaeological and mineralogical surveying in the metal-rich zones of Turkey.
One of the results of these surveys was the solution of a major enigma puzzling scholars for decades-a source of the elusive tin of antiquity. Why was tin so important in antiquity? It is tin, when alloyed with copper up to 5-l0%, that produces a good bronze. Its economic role in metal technology, at the time prior to the introduction of iron, is perhaps akin to that of oil in industry today. That is, it is the most important additive to the then high-tech metal of its age-bronze. The alternative form of alloy, made with arsenic (1-5%), became widespread in Anatolia in the fourth millennium and diminished with the use of tin alloys.
Geologists specializing in metals and minerals will often emphasize that tin or any other metal ore is never found in isolation of other metals. Each form part of a polymetallic universe in which man articulates his needs and thus should be archaeologically investigated within its multivariate space. Copper, lead, iron, silver, and gold were all part of the panoply of available metal ores in the resource zones that became the target of metal exploitation and exchange beginning in the aceramic Neolithic (eighth millennium B.C.). Although today all of these metals may seem commonplace, the ingenious ways metals were manipulated and manufactured, as well as the role the industry and metal trade played in the increasingly complex societies of the Bronze Age may come as a surprise. They all formed the basis of an incipient industrial revolution that subtly changed the way the environment was manipulated and in turn provided the backdrop for a number of other changes in institutional systems. This technological transformation occurred in the highlands of southwestern Asia-an area today encompassing modern Turkey, Iran, Caucasus, and the Balkans. That is, an "arc of metals."
This project focused on a search for the sources of these vital raw materials in Turkey-the birthplace of some of the earliest pyrotechnological innovations. The primary intent was to track down the direction and magnitude of the traffic in metals, and the impact of this trade on the producers of metals. The second goal was to understand the technological processes involved in the manufacture of tools, weapons, and ornaments in the Taurus area, a major source zone accessible to neighboring Syria, Mesopotamia, and the coastal Mediterranean. The target was to investigate the suites of crafts involved in the manufacture of metals and how ancient technologies articulated with economy, and how materials, personnel, and processes integrated across technologies. In other words, the objectives were multidimensional: where were the sources of metals, how were the metals made, and the socio-economic and political systems that impacted and in turn were changed by this industry.
The 1993 excavations were conducted under the auspices of the Turkish Ministry of Culture, Directorate General of Monuments and Museums, specifically the Ni©de Museum. Generous funds were provided by the National Endowment for the Humanities, the National Geographic Society, and the Institute of Aegean Prehistory. Close collaboration and funds for analysis were provided by the Smithsonian Institution, Conservation Analytical Laboratory, the Turkish Geological Survey (MTA), the Historical Metallurgy Society of England, and Bo©aziçi University in Istanbul.
Göltepe is located two kilometers opposite Kestel mine on top of a large battleship-shaped natural hill four kilometers from Çamard1 in south-central Turkey. The natural hill measures close to sixty hectares total and is fortified at the summit, with cultural deposition throughout the entire extent of its surface (fig. 1). Uncalibrated 14C dates from the 1990 season range from 3290-1840 B.C. Architecturally, unlike any site in Turkey, the workshop/habitation units were semi-subterranean and fully subterranean pit-houses. The pit-houses were cut into the graywacke bedrock with smaller subsidiary pits in association with it. Smaller houses measure four to six meters in diameter. Larger units are nine by five meters and are terraced off the slope, much like the present day village, Celaller. The superstructure of these units are wattle and daub and a number of branch impressions on mud were found this year. Unique also are what appear to be architectural features-geometrically designed terra-cotta panels which may have decorated the interior spaces of the pit-houses (fig. 2).
Determining the horizontal extent of the site was an important goal for the 1993 season, since a size of sixty hectares is an anomaly in such an agriculturally unfavorable environment. In previous years, subsurface features were mapped by magnetic resistivity sampling in tandem with one by one meter test pits in an attempt to determine the size of the site. This summer a backhoe operation was introduced. Thirty-six stratigraphic profile trenches were executed over the entire site. These strat-trenches were one meter wide and ten to twenty meters long; profiles were drawn for both sides of the trench. A couple of conclusions can now be drawn from this procedure: First, the circuit wall does surround the site, although in places it may also function as a terrace wall. Secondly, the perimeter of the site is now more in line with a believable areal size: the density of population walled in at the summit measures five hectares; less dense, scattered extra-mural settlement extends between eight and ten hectares. This is a conservative estimate and it is still possible that pit-houses were dug all over the landscape between the site and the mine. The spread of cultural material over the surface of the hill still measures sixty hectares; however, it is believed that most of this is due to erosion. The limitations of the backhoe are that if the plow went over a pit-house, it was included in the hectarage, if not, then only surface scatter betrays the probability there may be pit-houses below. These estimates, of course, do not include Kestel mine, or its one kilometer slope area, where evidence of structures and contemporary pottery was also found. Thus, linked together as a man-mine system, the sixty hectares total is probably closer to reality.
Four larger horizontal areas were also exposed on the summit: Trenches B05/B06, Trenches E62-E67/E69/E70, Trenches C16/C01/C02/D67, and Trenches A15/A23/A24. The phasing for these exposures is as follows.
The earliest, Phases 3 and 4, are characterized as subterranean pit-house periods. Tentatively they correspond to the Early Bronze Age II period on the basis of pottery parallels with Tarsus. The bulk of the ceramics are burnished wares and clinky wares (Anatolian metallic).
Overlying these is Phase 2, a "wall" phase, which represents a period of expansion. Although pit-houses continue to be built, large above-ground walled structures were erected on top of large terraces constructed of colluvial stones. In Area E, only the terrace is preserved; the architectural plans of the structure were lost to erosion. The walls of Phase 2 buildings were often built over the underlying pit-houses, which were filled in with industrial debris. The circuit wall dates to this phase and corresponds roughly to Early Bronze Age III in Tarsus terms. At Tarsus there is an architectural break between Early Bronze Age II and Early Bronze Age III as well, when megaron-related structures appear. This is also the period when ceramic connections with Troy (such as the depas and wheel-turned pottery) appear in Tarsus. At Göltepe, pottery such as Syrian bottles and Syrian metallic wares, corrugated plain simple wares, and red-slipped red-burnished light clay wares (the depas ware type) are present and link the site ceramically with Cilicia and northern Syria. Present, too, are a number of Khirbet-Kerak (Karaz-Pulur) sherds, which were non-local.
The upper-most levels are dated to Phase 1. These are topsoil and transitional levels and represent collapse and site abandonment at the end of the third millennium B.C. In one restricted sector of the east slope, Iron Age reuse of Early Bronze Age pit-houses was also identified.
A number of artifacts were recovered on floor contexts. A substantial amount of ground tin ore was found inside ceramic vessels. Some ground powder may represent slag, which was ground to release the tin ore entrapped in the smelting process. An important aim this year was to define quantitatively processing parameters. Measurements were made of industrial debris. Some seventy kilograms of ore powder and fifty kilograms of ore nodules from excavated contexts were weighed. The total assemblage of crucible fragments from this season alone weighs one ton. In addition, chronological distinctions can now be made with the varieties of crucibles found in different sectors of the site, which will enable a clearer picture of how the industry changed through time to meet increasing demands for the product, tin. An earlier, smaller crucible type (seventeen to twenty centimeters in diameter) and a later, larger crucible (twenty to sixty centimeters in diameter) will be part of the database for a household assemblage investigation of craft production.
In conjunction with the above analytical programs, several replication experiments are now on-going to test the feasibility of the production model, the physical conditions required, and the expected end products. B. Earl of Cornwall and H. Özbal from Bo©aziçi University successfully smelted tin metal in 1992 utilizing tin powder found in Early Bronze Age II/III contexts. Enriching a low grade 1% cassiterite ore mixture to approximately 10% by vanning (panning with a shovel) with one cup of water, this charge was then placed in a homemade crucible made with local clay and chaff temper. The charge, which was found in cups from the floor of Early Bronze Age pit-houses, was placed in successive layers of charcoal, and after twenty minutes of blowing through a blowpipe, tin prills (globules) entrapped inside an envelope of glassy slag emerged inside the crucible. During this experiment tin metal prills encased in glassy slag were released by grinding with a lithic tool. The slag was thus in powder consistency and virtually invisible unless microscale sampling methods are introduced.
While it is recognized that cassiterite alone will smelt directly in a crucible, such a process requires reduction by carbon-rich gases and would generate little slag. Smelting thus results in a multi-step production of tin metal with refining accomplished by washing, grinding, and remelting. Although highly labor intensive, the smelting process is simple and does not require technical sophistication. The industry as a whole, however, does represent a sophistication typical of third millennium metallurgy in Anatolia. The skill of the ancient metallurgists was highlighted by a new find, a coiled necklace made of an unusual alloy: silver, tin, zinc, and copper (fig. 3). Other objects of metal, such as bronze and lead, as well as molds, were excavated from the pit-houses.
The work done this season has gone a long way towards couching intelligent questions regarding the context and organization of tin production in the region. Were specialist laborers operating out of a larger site and was it part of a more complex system, or was it a cottage-industry? The possibilities are interesting and quite varied.
The development of metallurgy in Anatolia was an exceedingly complex process. The results of lead isotope research suggest a traffic of metals-at least for lead, silver, and lead-containing copper based artifacts. On the basis of over ten years of research in the central Taurus region, a multiplicity of metals are shown to have been extracted from these sources. A much clearer picture of the history of the resource zones is beginning to emerge than was heretofore possible. It is now evident, for example, that neither the development of lowland prestate societies nor the emergence of complex urban centers can be understood in isolation. Rather, throughout most of their history, the lowlands and highlands were interconnected and intertwined by traders and Bronze Age entrepreneurs. By closing a significant gap in our understanding of metal production at a site within a strategic metal zone, our research has become central to forthcoming interpretative efforts seeking to pull together the growing corpus of metals from urban centers. In so doing, our work will illuminate the metallurgical development of a little-known region that was surely of fundamental importance to the entire ancient Near East.
K. Aslihan Yener joined the faculty of the Oriental Institute in July 1993 and is currently teaching courses in Syro-Anatolian archaeology.
Revised: February 7, 2007