Arsenopyryt

Arsenopyryt, also known as arsenopyrite (chemical formula FeAsS), is an iron arsenic sulfide mineral and one of the most common arsenic-bearing minerals found in hydrothermal ore deposits. It typically forms in high-temperature veins associated with other sulfides and can occur in metamorphic rocks as well. The name reflects its content of arsenic.

Physically, arsenopyryt has a metallic luster and a steel-gray to gray-black color. Its streak is gray, and it is relatively hard, with a Mohs hardness of about 5.5 to 6. Its density ranges around 5.9 to 6.2 g/cm3. Crystals are often prismatic and elongated, and while crystalline forms are common, it is frequently found in compact or radiating aggregates. The mineral is opaque and can tarnish to dull brownish hues on exposure.

Geologically, arsenopyryt occurs in a wide range of settings, including hydrothermal veins, greisens, and contact metamorphic zones. It commonly associates with pyrite, pyrrhotite, chalcopyrite, sphalerite, galena, and stibnite. It is widely distributed around the world and can be an indicator of hydrothermal ore systems. In some gold and precious metal deposits, arsenopyryt may occur with tellurides or native gold, though it is not itself a primary source of gold.

Economically, arsenopyryt is the principal arsenic-bearing mineral and a primary source of arsenic in ore processing. The ore often requires careful handling and processing due to its arsenic content, which poses environmental and health risks if not managed properly. Safety and regulatory controls are important in mining and refining operations dealing with arsenopyryt-bearing ore.