Copper is the metal of Venus in the classical scheme, and the pairing rests on both appearance and mythic geography: copper takes a warm reddish and, when it weathers, a beautiful green patina, and its great ancient source was Cyprus, the island sacred to Aphrodite, indeed the Latin name of the metal, cuprum, derives from Cyprus. The alchemists marked copper and Venus with the same symbol, the circle above a cross that also serves as the sign for the female.
Copper's green corrosion products, verdigris and malachite, tie it to the green of Venus and to the cosmetic and pigment traditions. As the first metal widely worked by humans, and the basis, alloyed with tin, of bronze, copper stands near the beginning of metallurgy. Its Venusian symbolism gives it associations of love, beauty, harmony and the arts, and in ritual and folk practice copper is linked to attraction and to healing; it is also, unlike most of the seven, an excellent conductor, a property that has given it a large modern metaphysical literature of its own.
Sources The Secrets of AlchemyLawrence M. Principe with The Oxford English Dictionary, 3rd editionOxford University Press