Proustite is a

sulfosalt Sulfosalt minerals are sulfide minerals with the general formula , where *A represents a metal such as copper, lead, silver, iron, and rarely mercury, zinc, vanadium *B usually represents semi-metal such as arsenic, antimony, bismuth, and rarely ...

mineral In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid chemical compound with a fairly well-defined chemical composition and a specific crystal structure that occurs naturally in pure form.John P. Rafferty, ed. (2 ...

consisting of

silver Silver is a chemical element with the symbol Ag (from the Latin ', derived from the Proto-Indo-European ''h₂erǵ'': "shiny" or "white") and atomic number 47. A soft, white, lustrous transition metal, it exhibits the highest electrical ...

sulfarsenide, Ag₃ As S₃, known also as light red silver or ruby silver ore, and an important source of the metal. It is closely allied to the corresponding sulfantimonide,

pyrargyrite Pyrargyrite is a sulfosalt mineral consisting of silver sulfantimonite, Ag3SbS3. Known also as dark red silver ore or ruby silver, it is an important source of the metal. It is closely allied to, and isomorphous with, the corresponding sulfarse ...

, from which it was distinguished by the chemical analyses of Joseph L. Proust (1754–1826) in 1804, after whom the mineral received its name. The prismatic crystals are often terminated by the scalenohedron and the obtuse rhombohedron, thus resembling calcite (dog-tooth-spar) in habit. The color is scarlet-

vermilion Vermilion (sometimes vermillion) is a color, color family, and pigment most often made, since antiquity until the 19th century, from the powdered mineral cinnabar (a form of mercury sulfide, which is toxic) and its corresponding color. It i ...

and the luster adamantine;

crystal A crystal or crystalline solid is a solid material whose constituents (such as atoms, molecules, or ions) are arranged in a highly ordered microscopic structure, forming a crystal lattice that extends in all directions. In addition, macro ...

s are

transparent Transparency, transparence or transparent most often refer to: * Transparency (optics), the physical property of allowing the transmission of light through a material They may also refer to: Literal uses * Transparency (photography), a still, ...

and very brilliant, but on exposure to light they soon become dull black and opaque. The streak is scarlet, the hardness 2 to 2.5, and the

specific gravity Relative density, or specific gravity, is the ratio of the density (mass of a unit volume) of a substance to the density of a given reference material. Specific gravity for liquids is nearly always measured with respect to water at its densest ...

5.57. Its transparency differs from specimen to specimen, but most are opaque or translucent. Proustite occurs in

hydrothermal Hydrothermal circulation in its most general sense is the circulation of hot water (Ancient Greek ὕδωρ, ''water'',Liddell, H.G. & Scott, R. (1940). ''A Greek-English Lexicon. revised and augmented throughout by Sir Henry Stuart Jones. with th ...

deposits as a phase in the oxidized and supergene zone. It is associated with other silver minerals and sulfides such as native silver, native arsenic,

xanthoconite Xanthoconite is a sulfosalt mineral with the chemical formula Silver, Ag3Arsenic, AsSulfur, S3. References

Sulfosalt minerals Silver minerals Monoclinic minerals Minerals in space group 15 Minerals described in 1840 {{mineral-stub ...

stephanite Stephanite is a silver antimony sulfosalt mineral with formula: Ag5 Sb S4. It is composed of 68.8% silver, and sometimes is of importance as an ore of this metal. History Under the name Schwarzerz it was mentioned by Georgius Agricola in 1546, an ...

acanthite Acanthite is a form of silver sulfide with the chemical formula Ag2S. It crystallizes in the monoclinic system and is the stable form of silver sulfide below . Argentite is the stable form above that temperature. As argentite cools below that tem ...

, tetrahedrite and chlorargyrite. Magnificent groups of large crystals have been found at

Chañarcillo Chañarcillo is a town and mine in the Atacama Desert of Copiapó Province, Atacama Region, Chile, located near Vallenar and 60 km from Copiapó. It is noted for its silver mining. The town grew up after the Chañarcillo silver mine was discovere ...

Chile Chile, officially the Republic of Chile, is a country in the western part of South America. It is the southernmost country in the world, and the closest to Antarctica, occupying a long and narrow strip of land between the Andes to the east a ...

; other localities which have yielded fine specimens are

Freiberg Freiberg is a university and former mining town in Saxony, Germany. It is a so-called ''Große Kreisstadt'' (large county town) and the administrative centre of Mittelsachsen district. Its historic town centre has been placed under heritage c ...

and

Marienberg Marienberg is a town in Germany. It was the district capital of the Mittlerer Erzgebirgskreis (Central Ore Mountains district) in the southern part of Saxony, and since August 2008 it has been part of the new district of Erzgebirgskreis. As of ...

Saxony Saxony (german: Sachsen ; Upper Saxon: ''Saggsn''; hsb, Sakska), officially the Free State of Saxony (german: Freistaat Sachsen, links=no ; Upper Saxon: ''Freischdaad Saggsn''; hsb, Swobodny stat Sakska, links=no), is a landlocked state of ...

, Joachimsthal in Bohemia and

Sainte-Marie-aux-Mines Sainte-Marie-aux-Mines (; ; Alsatian: ''Màrkìrisch'') is a commune in the Haut-Rhin department and Grand Est region of north-eastern France. Geography Sainte-Marie-aux-Mines is located in the massif of the Vosges Mountains, where it occupie ...

Alsace Alsace (, ; ; Low Alemannic German/ gsw-FR, Elsàss ; german: Elsass ; la, Alsatia) is a cultural region and a territorial collectivity in eastern France, on the west bank of the upper Rhine next to Germany and Switzerland. In 2020, it had ...

. File:Proustite (long prismatic crystal) - Chanarcillo, Copiapo Province, Atacama Region, Chile.jpg, Proustite (long prismatic crystal) - Chañarcillo, Copiapo Province, Chile. Specimen height is 4 cm.

Structure

References

{{1911, wstitle=Proustite, volume=22, page=490 Silver minerals Arsenic minerals Sulfosalt minerals Trigonal minerals Minerals in space group 167

Structure

See also

References