Arsenopyrite - FeAsS

Habit: Crystals flat tabular to blocky to prismatic, striated. Also compact, granular and columnar. Silver-white to steel-gray, can tarnish, giving it a brownish or pink color. Metallic Luster, opaque. Associated with significant amounts of gold.

Environment: Occurs mostly in high-temperature Hydrothermal veins, in Pegmatites and contact metamorphic deposits

Etymology: Named from the older term for the mineral, arsenical pyrites. Arseniopyrite is the most common arsenic mineral.