Acanthite
Image: Didier Descouens (CC BY-SA 3.0)
Mineral NameAcanthite
Chemical FormulaAg₂S
Mohs Hardness2.5
Crystal Systemmonoclinic
Lustermetallic
Streak Colorblack to grayish black
Cleavageindistinct
Fractureconchoidal to uneven
Specific Gravity7.2
Colorsdark gray, black
Transparencyopaque
Type LocalityAbraham Shaft, Himmelfahrt Mine, Freiberg District, Erzgebirge, Saxony, Germany
Mineral GroupSulfides
Usesore of silver, collector
Associated Mineralscalcite
Rarityuncommon
Description
This specimen features dark gray to black acanthite crystals, some appearing as small, blocky forms and others as delicate, wire-like structures, embedded within a matrix of white to off-white botryoidal calcite.
Geological Context
Acanthite typically forms in low-temperature hydrothermal veins, often associated with other silver minerals, in the oxidation zone of silver deposits. It is a primary ore mineral for silver.
