Enargite

Enargite is a copper arsenic sulfide mineral with the chemical formula Cu3AsS4. It belongs to the sulfosalt mineral group and forms in hydrothermal vein systems rich in copper and arsenic. Enargite crystals are typically orthorhombic and occur as prismatic, tabular, or lamellar aggregates, though it is also found in massive crusts.

In hand sample, enargite has a metallic to submetallic luster and a dark gray to black coloration that can show a brownish or purplish tint in polished surfaces. The streak is gray to gray-black. It tends to have imperfect cleavage and a relatively high density. Hardness on the Mohs scale is about 3.5 to 4, making it a softer mineral for metallic sulfides.

Chemically, enargite contains copper, arsenic, and sulfur, and it can be an important source of copper in some ore deposits. However, its arsenic content requires careful handling during mining and processing due to toxicity. Enargite commonly occurs alongside other copper sulfides such as pyrite and chalcopyrite, as well as arsenic-bearing minerals like realgar and orpiment, in hydrothermal veins and replacements.

Worldwide occurrences include various copper-rich ore deposits where hydrothermal activity has concentrated copper, arsenic, and sulfur. Enargite is primarily of interest to mineral collectors and ore processors, rather than a primary ore in most mining districts.