mohawkite

thumb|right|Polished mohawkite nugget thumb|Mohawkite nugget

Mohawkite is a rare rock consisting of mixtures of arsenic, silver, nickel, skutterudite and copper, with the formula Cu3As up to Cu6As, and the most desirable material was usually found in a 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.