Mohawkite

Mohawkite is a rare rock consisting of mixtures of arsenic and copper, with the formula Cu₃As up to Cu₆As, usually in white quartz matrix. It has a hardness of 3-3.5 and a metallic luster. It is named after the Mohawk mine where it was originally found. Colors range from brassy-yellow to metallic gray, and sometimes will have a blue or greenish surface tarnish. These colors come from its two main ingredients, the arsenic-rich copper minerals algodonite and domeykite. Its color may resemble pyrrhotite, but unlike pyrrhotite, mohawkite is not magnetic.