Dictionary:

argentite

  (är'jən-tīt')

A valuable silver ore, Ag₂S, with a lead-gray color and metallic luster that is often tarnished a dull black.

Environment

In fairly low-temperature ore veins formed at some distance from the primary source.

Frequently occurs in poorly formed, dull black crystals, usually cubic but often so distorted and branching that it is difficult to recognize their faces. Commonly massive.

Dark lead gray. Luster metallic, usually tarnished to dull black; hardness 2-2Ɖ; specific gravity 7.3; fracture subconchoidal; cleavage poor cubic and dodecahedral. Like lead, can be cut by a knife (sectile).

Silver sulfide (87.1% Ag, 12.9% S).

Blowpipe fuses it into a bead on charcoal, which in an oxidizing flame gives silver button. Tests for silver then apply.

Sectility distinguishes it from other sulfides, particularly galena (which shows far better brittle cleavage). Grayer color distinguishes it from very white native silver; colorless nitric acid solution distinguishes it from chalcocite; copper nitrate solution is green.

Argentite is the most important primary ore of silver. Of common occurrence in veins with native silver. It seems to have catalytic power, with wire silver appearing to rise from argentite crystal surfaces. Fine crystals are found in Mexico, in Saxony, at Kongsberg, Norway, and at Cobalt, Ontario. Encountered near the surface of ore veins; there are no good commercial occurrences remaining in the U.S.

Argentite has a cubic structure only at temperatures above 180°C, so its presence indicates that the vein formed at temperatures higher than 180°C. Actually all Ag ₂ S specimens are structurally rearranged into acanthite (orthorhombic Ag ₂ S) at room temperature and are now pseudomorphs after the original cubic argentite.

The noun has one meaning:

Meaning #1: a valuable silver ore consisting of silver sulfide (Ag2S)

Argentite

The unit cell of argentite

Argentite, a mineral which belongs to the galena group, is cubic silver sulfide (Ag₂S). It is occasionally found as uneven cubes and octahedra, but more often as dendritic or earthy masses, with a blackish lead-grey color and metallic lustre. The cubic cleavage, which is so prominent a feature in galena, here present only in traces. The mineral is perfectly sectile and has a shining streak; hardness 2.5, specific gravity 7.3. It occurs in mineral veins, and when found in large masses, as in is Mexico and in the Comstock Lode in Nevada, it forms an important ore of silver. The mineral was mentioned 1529 by G. Agricola, but the name argentite (from the Lat. argentum, silver) was not used till 1845 and is due to W. Haidinger. Old names for the species are Glaserz, silver-glance and vitreous silver. A cupriferous variety, from Jalpa in Mexico, is known as jalpaite.

Acanthite, also Ag₂S, crystallizes in the monoclinic system and is the stable form below 177^oC. As argentite cools below that temperature its cubic form is distorted to the monclinic form of acanthite.

References

• Mindat.org
• Webmineral.org
• This article incorporates text from the Encyclopædia Britannica Eleventh Edition, a publication now in the public domain.

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