Mining in Cornwall and Devon tin was found as alluvial deposits of cassiterite in the gravels of stream beds. Eventually tin was mined underground; underground mines sprang up as early as the 16th century. Tin lodes were also found in outcroppings of cliffs. Tin is one of the earliest metals to have been exploited in Britain. Chalcolithic metal workers discovered that by putting a small proportion of tin (5 – 20%) in molten copper, the alloy bronze was produced. The alloy is harder than copper. The oldest production of tin-bronze is in Turkey about 3500 BC, but exploitation of the tin resources in Britain is
Liberty Bell Museum found a considerably higher level of tin in the Liberty Bell than in other Whitechapel bells of that era, and suggested that Whitechapel made an error in the alloy, perhaps by using scraps with a high level of tin to begin the melt instead of the usual pure copper. The analysis found that, on the second recasting, instead of adding pure tin to the bell metal, Pass and Stow added cheap pewter with a high lead content, and incompletely mixed the new metal into the mold. The result was "an extremely brittle alloy which not only caused the Bell