<P> 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 . </P> <P> 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 . </P> <P> Tin extraction and use can be dated to the beginning of the Bronze Age around 3000 BC, 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 . </P>

Where did tin come from in the bronze age