Kestel is a probable site of Bronze Age tin mining in the Taurus Mountains in ancient Anatolia (now Turkey). Tin was as scarce and valuable as petroleum is today in the Bronze Age. It was a vital ingredient of bronze, used with copper to make the alloy.
K. Aslihan Yener spent years in archaeometallurgy surveys together with the Turkish Geological Survey (MTA) and found cassiterite (tin ore) crystals in a stream in the Taurus foothills. This ore is purple; previous searches had been looking for black ore because most tin ores are black. Near the site was a deserted valley with a hill called Kestel that proved to hold a tin mine. Additionally, fragments of Bronze Age pottery were found in and near the mine. Inside, there were veins of bright purple tin ore.
The Kestel mine has two miles (3 km) of tunnels, many of which are only about two feet wide, just large enough to allow children to do the mining work. In one abandoned shaft, a burial of twelve to fifteen children was found, presumably killed while working in the mine.
In 1989, on a hill opposite the mine, associates found piles of Bronze Age pottery, close to 50,000 ground stone tools and evidence that this site had been continuously occupied from 3290–1840 BC. A great deal of the city was semi subterranean. The pottery at the site (named Göltepe) provided the final proof of the tin industry in the Bronze Age. Many thick crucibles lined with slag were found at the site and tests revealed the slag to have very high concentrations of tin (30% to almost 100%). It is likely that after the ore nuggets were washed, stone tools were used to grind them to a powder, and then the powder was heated to melt out the tin. All of this can be accomplished with Bronze Age tools and methods. This was somewhat surprising because early Assyrian records indicated that they imported tin into Anatolia, suggesting that the area did not have a supply of its own. In turn, the Assyrians imported large quantities of tin from Afghanistan. The Kestel mine stopped producing at the end of the third millennium BC.