Arsenopyrite
Image: Islam90 (CC BY-SA 4.0)
Mineral NameArsenopyrite
Chemical FormulaFeAsS
Mohs Hardness5.5
Crystal Systemmonoclinic
Lustermetallic
Streak Colordark grayish-black
Cleavagedistinct on {101}
Fractureuneven
Specific Gravity6
Colorssilvery white, steel gray, yellowish (tarnished)
Transparencyopaque
Type LocalityWidespread, notable localities include Freiberg (Germany), Panasqueira (Portugal), various localities in Sweden, Bolivia, Canada, and the USA.
Mineral Groupsulfides
Usesore of arsenic, minor ore of gold, collector
Associated Mineralspyrite, chalcopyrite, sphalerite, galena, quartz, gold
Raritycommon
Description
Arsenopyrite typically appears as silvery-white to steel-gray metallic crystals, often prismatic or tabular, which may tarnish to a duller gray or yellowish hue. The image shows a microscopic view of a polished section, appearing yellowish under normal light and bright white under polarized light, with numerous fractures.
Geological Context
This mineral is commonly found in high-temperature hydrothermal veins, contact metamorphic deposits, and pegmatites. It often forms in association with other sulfide minerals and can serve as an indicator mineral for gold mineralization.
