Acanthite
Image: Robert M. Lavinsky (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
Colorslead-gray, iron-black
Transparencyopaque
Type LocalityBanská Štiavnica Mines, Banská Štiavnica, Banská Bystrica Region, Slovakia
Mineral GroupSulfides
Usessilver ore, collector
Associated Mineralsnative silver, galena, sphalerite, pyrite, quartz, calcite
Raritycommon
Description
This image displays a dark, metallic specimen of acanthite, likely a massive or botryoidal aggregate, exhibiting its characteristic lead-gray to black color and metallic luster.
Geological Context
Acanthite is a common secondary mineral found in low-temperature hydrothermal silver deposits. It often forms as a pseudomorph after argentite, its high-temperature cubic polymorph, upon cooling.
