Enargite is a mineral that contains both copper and arsenic.

Chemical Formula: Cu3AsS4
Class: Sulfosalt
Hardness: 3
Coloration: Grayish black to iron black

How to identify it/Unique Characteristics or Properties: Enargite is a mineral that contains both copper and arsenic. It is recognizable by its distinctive crystals, which start off metallic black but on exposure to light it loses its shine and dulls to the crystals you see in the picture to the right. Crystals can range from small to quite large, usually tabular and stocky. Other arsenic heavy minerals include realgar and orpiment.

Where to it find in…

The Northwest: Butte Montana, Colorado
Other: Chili, Italy, Taiwan, Peru
Past Uses: Mainly used as an arsenic ore, but also sometimes mined for its copper content.
How it was Made: Forms in veins of other minerals.
Interesting Facts: Some rare examples of this mineral has its crystals form a star shape.