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Tin is an essential metal in the creation of tin bronzes, and its acquisition was an important part of ancient cultures from the Bronze Age onward. Its use began in the Middle East and the Balkans around 3000 BC. Tin is a relatively rare element in the Earth's crust, with about 2 parts per million (ppm), compared to iron with 50,000 ppm, copper with 70 ppm, lead with 16 ppm, arsenic with 5 ppm, silver with 0.1 ppm, and gold with 0.005 ppm (Valera & Valera 2003, p. 10). Ancient sources of tin were therefore rare, and the metal usually had to be traded over very long distances to meet demand in areas which lacked tin deposits.
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Known sources of tin in ancient times include the southeastern tin belt that runs from Yunnan in China to the Malay Peninsula; Devon and Cornwall in England; Brittany in France; the border between Germany and the Czech Republic; Spain; Portugal; Italy; and central and South Africa (Wertime 1979, p. 1; Muhly 1979). Syria and Egypt have been suggested as minor sources of tin, but the archaeological evidence is inconclusive.
Early use
Tin extraction and use can be dated to the beginning of the Bronze Age around 3000 BCE, during which copper objects formed from polymetallic ores had different physical properties (Cierny & Weisgerber 2003, p. 23). The earliest bronze objects had tin or arsenic content of less than 2% and are therefore believed to be the result of unintentional alloying due to trace metal content in copper ores such as tennantite, which contains arsenic (Penhallurick 1986, p. 4). The addition of a second metal to copper increases its hardness, lowers the melting temperature, and improves the casting process by producing a more fluid melt that cools to a denser, less spongy metal (Penhallurick 1986, pp. 4–5). This was an important innovation that allowed for the much more complex shapes cast in closed molds of the Bronze Age. Arsenical bronze objects appear first in the Middle East where arsenic is commonly found in association with copper ore, but the health risks were quickly realized and the quest for sources of the much less hazardous tin ores began early in the Bronze Age (Charles 1979, p. 30). This created the demand for rare tin metal and formed a trade network that linked the distant sources of tin to the markets of Bronze Age cultures.
Cassiterite (SnO2), oxidized tin, most likely was the original source of tin in ancient times. Other forms of tin ores are less abundant sulfides such as stannite that require a more involved smelting process. Cassiterite often accumulates in alluvial channels as placer deposits due to the fact that it is harder, heavier, and more chemically resistant than the granite in which it typically forms (Penhallurick 1986). These deposits can be easily seen in river banks, because cassiterite is usually black or purple or otherwise dark, a feature exploited by early Bronze Age prospectors. It is likely that the earliest deposits were alluvial and perhaps exploited by the same methods used for panning gold in placer deposits.
Archaeological importance
The importance of tin to the success of Bronze Age cultures and the scarcity of the resource offers a glimpse into that time period's trade and cultural interactions, and has therefore been the focus of intense archaeological studies. However, a number of problems have plagued the study of ancient tin such as the limited archaeological remains of placer mining, the destruction of ancient mines by modern mining operations, and the poor preservation of pure tin objects due to tin disease or tin pest. These problems are compounded by the difficulty in provenancing tin objects and ores to their geological deposits using isotopic or trace element analyses. Current archaeological debate is concerned with the origins of tin in the earliest Bronze Age cultures of the Near East (Penhallurick 1986; Cierny & Weisgerber 2003; Dayton 1971; Giumlia-Mair 2003; Muhly 1979; Muhly 1985).
Ancient trade
Due to the scattered nature of tin deposits around the world and its essential nature for the creation of tin bronze, tin trade played an important role in the development of cultures throughout ancient times. Archaeologists have reconstructed parts of the extensive trade networks of ancient cultures from the Bronze Age to modern times using historical texts, archaeological excavations, and trace element and lead isotope analysis to determine the origins of tin objects around the world (Valera & Valera 2003; Rovia & Montero 2003; Maddin 1998).
Mediterranean
The earliest sources of tin in the Early Bronze Age in the Near East are still unknown and the subject of much debate in archaeology (Dayton 1971; Dayton 2003; Maddin 1998; Muhly 1973; Penhallurick 1986; Stech & Pigott 1986; Kalyanaraman 2010). Possibilities include minor now-depleted sources in the Near East, trade from Central Asia (Muhly 1979), Sub-Saharan Africa (Dayton 2003), Europe, or elsewhere.
It is possible that as early as 2500 BCE, Erzgebirge had begun exporting tin, using the well established Baltic amber trade route to supply Scandinavia as well as the Mediterranean with tin (Penhallurick 1986, pp. 75–77). By 2000 BCE, the extraction of tin in Britain, France, Spain, and Portugal had begun and tin was traded to the Mediterranean sporadically from all these sources. Evidence of tin trade in the Mediterranean can be seen in a number of Bronze Age shipwrecks containing tin ingots such as the Uluburun off the coast of Turkey dated 1300 BCE which carried over 300 copper bars weighing 10 tons, and approximately 40 tin bars weighing 1 ton (Pulak 2001). While Sardinia does not appear to have much in terms of significant sources of tin, it does have rich copper and other mineral wealth and served as a centre for metals trade during the Bronze Age and likely actively imported tin from the Iberian Peninsula for export to the rest of the Mediterranean (Lo Schiavo 2003).
By classical Greek times, the tin sources were well established. Greece and the Western Mediterranean appear to have traded their tin from European sources, while the Middle East acquired their tin from Central Asian sources through the Silk Road (Muhly 1979, p. 45). For example, Iron Age Greece had access to tin from Iberia by way of the Phoenicians who traded extensively there, from Erzgebirge by way of the Baltic Amber Road overland route, or from Brittany and Cornwall through overland routes from their colony at Massalia (modern day Marseilles) established in the 6th century BCE (Penhallurick 1986). In 450 BCE, Herodotus described tin as coming from Northern European islands named the Cassiterides along the extreme borders of the world, suggesting very long distance trade, likely from Britain, northwestern Iberia, or Brittany, supplying tin to Greece and other Mediterranean cultures (Valera & Valera 2003, p. 11). It should be noted that the idea that the Phoenicians went to Cornwall for its tin and supplied it to the whole of the Mediterranean has no archaeological basis and is largely considered a myth (Penhallurick 1986, p. 123).
The early Roman world was mainly supplied with tin from its Iberian provinces of Gallaecia and Lusitania and to a lesser extent Tuscany. Pliny mentions that in 80 BCE, a senatorial decree halted all mining on the Italian Peninsula, stopping any tin mining activity in Tuscany and increasing Roman dependence on tin from Brittany, Iberia, and Cornwall. After the Roman conquest of Gaul, Brittany’s tin deposits saw intensified exploitation after the first century BCE (Penhallurick 1986, pp. 86–91). With the exhaustion of the Iberian tin mines, Cornwall became a major supplier of tin for the Romans after the 3rd century CE (Gerrard 2000).
Throughout the medieval period, demand for tin increased as pewter gained popularity. Brittany and Cornwall remained the major producers and exporters of tin throughout the Mediterranean through to modern times (Gerrard 2000).
Asia
Near Eastern development of bronze technology spread across Central Asia by way of the Eurasian Steppes, and with it came the knowledge and technology for tin prospection and extraction. By 2000 to 1500 BCE Uzbekistan, Afghanistan, and Tajikistan appear to have exploited their sources of tin, carrying the resources east and west along the Silk Road crossing Central Asia (Cierny & Weisgerber 2003, p. 28). This trade link likely followed an existing trade route of lapis lazuli, a highly prized semi-precious blue gemstone, and chlorite vessels decorated with turquoise from Central Asia that have been found as far west as Egypt and that date to the same period (Giumlia-Mair 2003, p. 93).
In China, early tin was extracted along the Yellow River in Erlitou and Shang times between 2500 and 1800 BCE. By Han and later times, China imported its tin from what is today Yunnan province. This has remained China’s main source of tin throughout history and into modern times (Murowchick 1991).
It is unlikely that Southeast Asian tin from Indochina was widely traded around the world in ancient times as the area was only opened up to Indian, Muslim, and European traders around 800 CE (Penhallurick 1986, p. 51).
Roman trade to India is well known from historical texts such as Pliny’s Natural History (book VI, 26), and tin is mentioned as one of the resources being exported from Rome to Southern Arabia, Somaliland, and India (Penhallurick 1986, p. 53; Dayton 2003, p. 165).