Domeykite

Domeykite is a copper arsenide mineral with the chemical formula Cu₃As. It is an opaque, metallic mineral that typically occurs in massive or botryoidal forms, but also rarely as small crystals. Its color ranges from tin-white to grey or yellowish-brown as it weathers.

Domeykite is found in hydrothermal veins and contact metamorphic zones, often associated with other copper minerals such as chalcocite, bornite, and native copper. It is a relatively rare mineral, named in 1845 after Ignacy Domeyko (Ignacio Domeyko), a Polish mineralogist and geologist who worked extensively in Chile.

Notable occurrences of domeykite include Chile, Germany, and the United States (Michigan, Arizona). While it is primarily a mineralogical specimen, it can be a minor ore of copper. When heated, domeykite emits a garlic-like odor due to the arsenic content. It has a hardness of 3-3.5 on the Mohs scale and a specific gravity of 7.2 to 7.9.