william foshag

Malachite and Azurite

You know how copper turns green when it’s left to oxidize? That process is what makes malachite green. It’s known as a copper carbonate hydroxide mineral, and is the source of most green paint pigments used until about 1800.

The rich blue mineral azurite (also one source of ancient paint pigments) is commonly found with malachite, and both are commonly found around large limestone deposits. Limestone is a form of aggregated calcium carbonate, and one of the primary sources of carbonate for both malachite and azurite formations. Arizona is the primary site where one can find malachite in North America. Malachite is more common than azurite, because it is far more stable to open air and sunlight.

Minerals from Earth and Sky, Part II: Gems and Gem Minerals. William F. Foshag, 1929.