Acanthite
Species
Uncommon · Ag₂S
Silver sulfide, iron black and soft enough to cut with a knife, the commonest silver mineral of low-temperature veins and enrichment zones. Above 173 °C it grows as the cubic form miners called argentite, which turns to acanthite on cooling but keeps the outline of the cube. Widespread in the silver mines of Saxony, Bohemia and Mexico; in Spanish America sulfide ores like it were amalgamated with mercury in the patio process, used at scale from 1554.
Identity
- Formula
- Ag₂S
- Chemical class
- Sulfide
- Also known as
- Argentite (cubic high-temperature form), Silver glance
- Ore of
- Silver
Crystallography
- Crystal system
- Monoclinic
- Habits
- Prismatic, Cubic, Octahedral, Massive
- Fracture
- Uneven
Physical properties
- Mohs hardness
- 2
- Density
- 7.2 g/cm³
- Luster
- Metallic
- Colors
- iron-black
- Streak
- black
- Transparency
- Opaque
Geology
- Origins
- Hydrothermal
- Host rocks
- Granite
- Associated minerals
- Silver, Pyrargyrite, Proustite, Galena, Chalcopyrite, Sphalerite, Calcite, Quartz
- Found in
- Hydrothermal vein (lode)
- Geography
- Czech Republic (Jáchymov), Germany (Freiberg, Schneeberg, Annaberg; St. Andreasberg), Mexico (Guanajuato, Zacatecas, Chihuahua), USA (Comstock Lode, Nevada), Chile (Chañarcillo), Canada (Cobalt, Ontario)
Classification
- Rarity
- Uncommon
- Gem quality
- No
Sources
- M. Pasero and others, IMA Commission on New Minerals, Nomenclature and Classification, The New IMA List of Minerals, updated September 2026. International Mineralogical Association (CNMNC), 2026.
- J. W. Anthony, R. A. Bideaux, K. W. Bladh, M. C. Nichols, Acanthite. Mineral Data Publishing, Handbook of Mineralogy, 2001.
- Acanthite. Wikipedia.
- Patio process. Wikipedia.
Browse the Crystal Encyclopedia — MGS Toolbox