2 : SULFIDES and SULFOSALTS (sulfides, selenides,
tellurides; arsenides, antimonides, bismuthides; sulfarsenites,
sulfantimonites, sulfbismuthites, etc.) B : Metal Sulfides, M: S > 1: 1 (mainly 2: 1)
A : With Cu, Ag, Au
Group. Isostructural with
Acanthite is the low-temperature version of Argentite.
crystals are rare, prismatic to long prismatic, elongated
along , to 2.5 cm, may be tubular; massive. Commonly
paramorphic after the cubic high-temperature phase (“argentite”),
of original cubic or octahedral habit, to 8 cm.
is a silver sulfide mineral and is one of the most important
ores of Silver. Acanthite
was named in 1855 by Gustav Adolf Kenngott from the Greek word
akantha meaning thorn, in allusion to its crystal shape.
The name Acanthite is often confused with, or used interchangably
with, Argentite. Acanthite and Agrentite have the same
chemistry, Ag2S, but different structures. Acanthite is the low-temperature form of Argentite.
Acanthite has a monoclinic structure and is stable below
173 degrees Celsius while Argentite has an isometric structure and is only stable at temperatures
173 degrees Celsius. All natural silver sulphide specimens (and gems) at room temperature are Acanthite.
The tarnish on sterling silver is chemically the same as Acanthite.
was named in 1855 by German
mineralogist Gustav Adolf Kenngott (1818-1897) from the Greek word
meaning thorn, in allusion to its crystal shape. It
was discovered in the Jáchymov District, Krušné Hory Mts, Karlovy Vary Region, Bohemia, Czech Republic.
distribution: widespread in silver deposits.
Localities for fine primary and paramorphic crystals
include: from Jáchymov (Joachimsthal), Czech
Republic [TL]. In Germany, at Freiberg, Schneeberg,
Annaberg, and Marienberg, Saxony; and from St. Andreasberg,
Harz Mountains. In Mexico, large paramorphs from Arizpe,
Sonora; in the Rayas and other mines at Guanajuato;
and from many mines in Zacatecas, Chihuahua, etc. In
the USA, at Butte, Silver Bow County, Montana; Tonopah,
Nye County, and the Comstock Lode, Virginia City, Storey
County, Nevada. From various mines at Cobalt, Ontario,
Canada. At Chañarcillo, south of Copiapó,
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