Arsenopyrite
Arsenopyrite is a sulfosalts / arsenide mineral recognized among collectors for its crystal form and distribution, with several world-class Chinese localities.
About Arsenopyrite
Arsenopyrite belongs to the sulfosalts / arsenide class in the arsenopyrite group and has the chemical formula FeAsS. It crystallizes in the monoclinic system and has a distinctive metallic presence in any collection. Its combination of structural character and global distribution make it a recognized species in both systematic and aesthetic collections.
Identification & care
Specimens usually show flat tabular to blocky, sometimes pseudo-octahedral ('lozenge') or rhombic cross-section; prismatic; also massive. Its color is typically silver-white to steel-gray, may have slight yellow tint and tarnished material often iridescent. The luster is metallic, sub-metallic, the streak is gray-black, and specimens are typically opaque. The cleavage is distinct/good on {001}; traces on {010}. The fracture is irregular/uneven, which aids identification.
Collector context
How it forms
The geological setting for Arsenopyrite is typically mesothermal gold-silver-arsenic hydrothermal veins; high-temperature sulfide ore deposits; metamorphic rocks associated with gold; often the most abundant arsenic mineral. It is commonly found in association with gold (microscopic inclusions — arsenopyrite is major gold host), pyrite, galena, sphalerite, chalcopyrite, löllingite.
Classic Chinese localities
**Yaogangxian W-Sn ore field** is a benchmark source for arsenopyrite. **Huanggang Fe-Sn deposit** is an important Chinese source for the species.
Why collectors care
Arsenopyrite is a frequently-sought species in serious collections because its habit is recognizable, its color often strong, and its best examples unmistakable even at a distance. Chinese material has driven much of the recent visual shift in the species — sharper crystals, deeper colors, cleaner matrix.
What affects value
Value in Arsenopyrite is assessed, in typical order of weight, against: (1) locality provenance; (2) size relative to the species norm; (3) crystal form and termination sharpness; (4) color saturation and zoning; (5) transparency and internal clarity; (6) matrix quality and aesthetic balance; (7) condition (absence of damage, chips, or repair). Cleaning quality and verified locality documentation act as multipliers across the above.
Naming history
The name Arsenopyrite has a specific etymological and historical context — see Mindat's reference entry for provenance details. We have retained naming data at the record level; published prose is paraphrased from factual fields rather than copied from source.