Lutzite

Lutzite is a mineral species that crystallizes in the monoclinic crystal system. It is a sulfide mineral, specifically an iron arsenic sulfide with the chemical formula FeAsS. It is an isometric polymorph of skutterudite. Lutzite is a relatively rare mineral that occurs in hydrothermal veins and pegmatites, often associated with other arsenic-bearing minerals. It typically forms as small, euhedral to subhedral crystals, or as granular masses. The color of lutzite is generally pale brass-yellow to steel-gray, and it possesses a metallic luster. Its streak is black. The hardness of lutzite on the Mohs scale is approximately 5 to 6, and its specific gravity is around 6.5. Lutzite is named in honor of the German mineralogist Wilhelm Lutz. When heated, it may sublime. It is not a common ore mineral, and its significance is primarily of mineralogical interest. It has been found in several locations worldwide, including Germany, Russia, and the United States.