Acanthite

Acanthite (Argentite); Image credit John Betts

Description

A gray to black metallic mineral of Silver sulfide. Acanthite occurs in hydrothermal deposits and as a corrosion product of Silver. Large crystals of acanthite have been mined in Norway (Kongsberg), Mexico (Pachuca, Guanajuato, Zacatecas) and the U.S. (Nevada, Colorado, Montana). On silver, acanthite crystals can appear as black, shiny, acanthus-like leaflets. At temperatures above 173 C, acanthite is converted to Argentite.

Synonyms and Related Terms

acanthus

Physical and Chemical Properties

• Luster = metallic
• Streak = black
• Cuts like lead; indistinct cleavage
• Composition = Ag2S
• CAS = 21548-73-2
• Mohs Hardness = 2.0 - 2.5
• Melting Point = 845 C
• Density = 7.2 - 7.4 g/ml
• Molecular Weight = 247.8

Risks

Sensitive to light.

Resources and Citations

• WebMineral: Acanthite

• Encyclopedia Britannica, http://www.britannica.com Comment: argentite" Accessed December 11, 2001, (gives conversion temperature as 91 C)

• C.W.Chesterman, K.E.Lowe, Audubon Society Field Guide to North American Rocks and Minerals, Alfred A. Knopf, New York, 1979 Comment: Gives conversion temperature (acanthite to argentite) as 173 C