|
| Acanthite
|
|
Discovered
in 1783; IMA
status:
Valid (pre-IMA; Grandfathered)
|
Composition: |
Silver |
87.06 % |
Ag |
|
|
|
Sulfur |
12.94 % |
S |
|
|
|
|
100.00 % |
|
|
|
|
|
Classification
|
|
|
Mineral
Classification: |
Sulfides
and Sulfosalts
|
Strunz 8th
Ed. ID:
|
2/B.05-10
|
Nickel-Strunz 10th
Ed. ID:
|
2.BA.35
|
|
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
|
Related
to: |
Acanthite
Group. Isostructural with
Aguilarite.
Acanthite is the low-temperature version of Argentite.
|
Members
of Group: |
Acanthite
Group:
Acanthite, Aguilarite, Cervelleite
|
Varieties: |
Zincian
Acanthite
|
Synonyms: |
Acantite,
Akanthite, α-Argentite, Argentite, Argentite-beta, Argentite-β,
Argyrite, Argyrose, Beta-Argentite, β-Argentite, Daleminzite,
Henkelite, ICSD 30445, Para-Silberglanz, PDF 14-72,
Silver Glance, Vitreous Silver
|
|
|
Crystal
Data
|
|
|
Crystallography:
|
Monoclinic - Prismatic
|
Crystal
Habit:
|
Primary
crystals are rare, prismatic to long prismatic, elongated
along [001], 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.
|
Twinning:
|
Polysynthetic
on {111}, may be very complex due to inversion; contact
on {101}
|
|
|
Physical
Properties
|
|
|
Cleavage: |
Indistinct,
none observed
|
Fracture: |
Irregular/uneven,
sub-conchoidal
|
Tenacity:
|
Sectile
|
Moh's
Hardness: |
2.0
- 2.5; Vickers: VHN100=21 - 25 kg/mm2
|
Density:
|
7.2
- 7.4 (g/cm3)
|
Luminescence:
|
None
|
Radioactivity:
|
Not
Radioactive
|
|
|
Optical
Properties
|
|
|
Color: |
Lead grey, iron
black
|
Transparency: |
Opaque
|
Luster: |
Metallic
|
Refractive
Index: |
R:
(400) 32.8, (420) 32.9, (440) 33.0, (460) 33.1, (480)
33.0, (500) 32.7, (520) 32.0, (540) 31.2, (560) 30.5,
(580) 29.9, (600) 29.2, (620) 28.7, (640) 28.2, (660)
27.6, (680) 27.0, (700) 26.4
|
Birefringence: |
n/a
(opaque)
|
Dispersion: |
n/a |
Pleochroism: |
n/a |
Anisotropism: |
Weak
|
|
|
Occurances
|
|
|
Geological
Setting: |
A
common silver species in moderately low-temperature
hydrothermal sulfide veins, and in zones of secondary
enrichment.
|
Common
Associations: |
Silver,
Pyrargyrite, Proustite, Polybasite, Stephanite, Aguilarite,
Galena, Chalcopyrite, Sphalerite, Calcite, Quartz
|
Common
Impurities: |
Se
|
Type
Locality: |
Jáchymov (St Joachimsthal),
Jáchymov District (St Joachimsthal), Krušné Hory Mts (Erzgebirge),
Karlovy Vary Region, Bohemia (Böhmen; Boehmen), Czech Republic
|
Year
Discovered: |
1855
|
View
mineral photos: |
Acanthite
Mineral Photos and Locations |
|
|
More
Information
|
|
|
|
Mindat.org
Webmineral.com
|
|
|
Acanthite
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
above
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.
Acanthite
was named in 1855 by German
mineralogist Gustav Adolf Kenngott (1818-1897) from the Greek word
άκανθα (ákantha)
meaning thorn, in allusion to its crystal shape. It
was discovered in the Jáchymov District, Krušné Hory Mts, Karlovy Vary Region, Bohemia, Czech Republic.
Acanthite
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,
Atacama, Chile.
|
Acanthite
gems for sale:
We
have not photographed our Acanthite
gems yet. Please
check back soon.
|
|