Arsenic

A semi-metallic substance of steel-gray color that forms a link between the metals and non-metallic bodies. It is found together with copper in some ore deposits, appearing as arsenical copper (copper alloyed with arsenic). This substance was valued and deliberately produced to improve casting properties and hardness, but was not important after the development of tin-bronze (tin alloyed with copper). It gave a very hard cutting edge to tools and weapons.

Metal, found as an impurity or major constituent in copper ores. Some Early Bronze Age copper contains more than 1 per cent and up to 7 per cent of arsenic, and should be classed as arsenical copper alloys.