Copper Mine
Copper alloy was mostly utilized in Roman Britain to make brooches, spoons, coins, statuettes and other things needed for armour. It was rarely used in it purest form; thus, it always contained other elements such as tin, zinc or lead, which added various properties to the alloy. Pure copper has a pinkish colour and, with the addition of a few percentage of other elements, its colour may change to pale brown, white or yellow.
The composition of copper alloy differed from region to region in the Roman Empire. Leaded and unleaded bronze were mainly used in the Mediterranean period. These types of bronze were produced by adding tin and lead to copper in certain amounts that depended on the type of object being produced.5% to 15% of tin was added to bronze for casting of most objects. Mirrors, on the other hand, were made with bronze that had approximately 20% tin as it needed a speculum, which is a silvery-white alloy.
Another copper alloy, brass, was not widely used in casting objects as it was very difficult to produce. The production of brass did not begin until the development of the cementation process. In this process, zinc ore and pure copper are heated in a sealed crucible. As the zinc ore is turned into zinc, the seal in the crucible traps the zinc vapour inside, which will then mix with the pure copper to produce brass. The production of brass through this process was controlled by 'state monopoly' as brass was being utilized for coins and military equipments. The production of sestertii and dupondii from brass was established by the Augustan period and brass was also utilized in production of other military fittings such as lorica segmentata.