 |
Chemical Formula | Ag2S |
|
Composition | Silver sulfide |
|
Color | Dark gray to nearly black. |
|
Streak | Black. Streak shiny |
|
Hardness | 2 |
|
Crystal Forms and Aggregates |
Acanthite crystallizes in the monoclinic system, and Argentite crystallizes in the
isometric system. However, the crystal structure of Argentite is unstable at temperatures below 356° F (180° C),
and when below that temperature its crystal structure
changes to that of Acanthite, but it retains the isometric crystals of Argentite. Therefore, Argentite
specimens are really Acanthite pseudomorphs after Argentite. Two types of Acanthite exist: monoclinic Acanthite (Acanthite that formed naturally as Acanthite, and is not a pseudomorph after Argentite) and Acanthite pseudomorph after Argentite. Monoclinic Acanthite occurs as distorted elongated prisms, and Acanthite pseudomorph after Argentite occurs as distorted groups of cubes, octahedrons, and dodecahedrons. However, both forms have the same crystal structure, and both are scientifically Acanthite. Crystals are usually in parallel groups. Aggregates include dendritic, as a coating, and massive. |
|
Transparency | Opaque |
|
Specific Gravity | 7.2 - 7.4 |
|
Luster | Metallic. Severe tarnish can cause it to become dull. |
|
Cleavage | 3, all sides. Indiscernible. |
|
Fracture | Subconchoidal |
|
Tenacity | Malleable and sectile |
|
Other ID Marks | Tarnishes dark gray |
|
Other Names |  Silver Glance |
|
In Group | Sulfides ; Simple sulfides |
|
All About | Specimens labeled as Argentite are sometimes sold by dealers. These specimens are really Acanthite pseudomorphs after Argentite, as Argentite cannot exist at normal temperatures (as explained above). |
|
Uses | Acanthite is perhaps the most significant ore of silver. Specimens commend a high price to collectors. |
|
Striking Features | Crystal aggregates, tarnish, and sectility |
|
Popularity (1-4) | 2 |
|
Prevalence (1-3) | 3 |
|
Demand (1-3) | 1 |
|
Distinguishing Similar Minerals |
Silver - lighter color, more malleable, not sectile Chalcocite - different fracture (conchoidal) Galena - good cleavage, different tarnish, no sectility |
|
Commonly Occurs With |
Barite, Bornite, Galena, Gold, Pyrargyrite, Pyrite, Silver |
|
Noteworthy Localities |
Fine specimens have come from Kongsberg, Norway, where it occurs with Silver. It also occurs in numerous places in Germany, notably the Clara and Wenzel mines in the Black Forest, and in Freiberg and Scheenberg, in Saxony, Germany. There are numerous localities in Mexico, most significant are Batopilas, in Chihuahua , where it occurs with Silver, and the Reyes Mine in Guanajuato. In the U.S., it occurs in the Comstock Lode, Virginia City, Nevada; Butte, Silver Bow Co., Montana; White Pine mine, Ontonagan Co., Michigan; Defiance mine, Inyo Co., California; and in the Alhambra mine, Grant Co., New Mexico. It occurs in numerous places in Colorado, in San Juan and Dolores Counties. |
|
Picture Icon Links |
Sorry. No Images currently available. |
|
Picture Links | Sorry. No Images currently available. |
