Pyrargyrite | |
---|---|
General | |
Category | Sulfosalt |
Formula (repeating unit) | Ag3SbS3 |
IMA symbol | Pyg [1] |
Strunz classification | 2.GA.05 |
Crystal system | Trigonal |
Crystal class | Ditrigonal pyramidal (3m) (same H-M symbol) |
Space group | R3c |
Unit cell | a = 11.047 Å, c = 8.719 Å; Z = 6 |
Identification | |
Color | Deep red to red gray |
Crystal habit | Include prismatic crystals with rhombohedral and scalenohedral faces forming terminations. massive, granular |
Twinning | Complex to lammellar |
Cleavage | Distinct on {1011}, imperfect on {0112} |
Fracture | Conchoidal, uneven |
Tenacity | Brittle |
Mohs scale hardness | 2.5 |
Luster | Adamantine |
Streak | dark cherry red |
Diaphaneity | Translucent to nearly opaque |
Specific gravity | 5.82 |
Optical properties | Uniaxial (–) |
Refractive index | nω = 3.084 nε = 2.881 |
Birefringence | δ = 0.203 |
Pleochroism | Distinct |
Other characteristics | Darkens upon exposure to light; crystals are frequently striated |
References | [2] [3] [4] |
Pyrargyrite is a sulfosalt mineral consisting of silver sulfantimonite, Ag3SbS3. Known also as dark red silver ore, ruby blende, garnete blende or ruby silver, it is an important source of the metal.
It is closely allied to, and isomorphous with, the corresponding sulfarsenide known as proustite or light red silver ore. Ruby silver or red silver ore (German Rotgültigerz) was mentioned by Georg Agricola in 1546, but the two species so closely resemble one another that they were not completely distinguished until chemical analyses of both were made.
Both crystallize in the ditrigonal pyramidal (hemimorphic-hemihedral) class of the rhombohedral system, possessing the same degree of symmetry as tourmaline. Crystals are perfectly developed and are usually prismatic in habit; they are frequently attached at one end, the hemimorphic character being then evident by the fact that the oblique striations on the prism faces are directed towards one end only of the crystal. Twinning according to several laws is not uncommon. The hexagonal prisms of pyrargyrite are usually terminated by a low hexagonal pyramid or by a drusy basal plane.
The color of pyrargyrite is usually greyish-black and the lustre metallic-adamantine; large crystals are opaque, but small ones and thin splinters are deep ruby-red by transmitted light, hence the name, from the Greek pyr and argyros, "fire-silver" in allusion to color and silver content, given by E. F. Glocker in 1831. The streak is purplish-red, thus differing markedly from the scarlet streak of proustite and affording a ready means of distinguishing the two minerals. The Mohs hardness is 2.75, and the specific gravity 5.85. The refractive indices (nω = 3.084 nε = 2.881) and birefringence (δ = 0.203) are very high. There is no very distinct cleavage and the fracture is conchoidal. The mineral occurs in metalliferous veins with calcite, argentiferous galena, native silver, native arsenic, etc. The best crystallized specimens are from Sankt Andreasberg in the Harz, Freiberg in Saxony, and Guanajuato in Mexico. Very high-quality pyrargyrite specimens were also found in the silver mines of Guadalcanal (Seville) and Hiendelaencina (Guadalajara), in Spain. [5] It is not uncommon in many silver mines in the United States, but rarely as distinct crystals; and it has been found in some Cornish mines.
Although the red silver ores afford a good example of isomorphism, they rarely form mixtures; pyrargyrite rarely contains as much as 3% of arsenic replacing antimony, and the same is true of antimony in proustite. Dimorphous with pyrargyrite and proustite respectively are the rare monoclinic species pyrostilpnite or fireblende (Ag3SbS3) and xanthoconite (Ag3AsS3): these four minerals thus form an isodimorphous group.
Greenockite, also cadmium blende or cadmium ochre (obsolete) is a rare cadmium bearing metal sulfide mineral consisting of cadmium sulfide (CdS) in crystalline form. Greenockite crystallizes in the hexagonal system. It occurs as massive encrustations and as hemimorphic six-sided pyramidal crystals which vary in color from a honey yellow through shades of red to brown. The Mohs hardness is 3 to 3.5 and the specific gravity is 4.8 to 4.9.
Vanadinite is a mineral belonging to the apatite group of phosphates, with the chemical formula Pb5(VO4)3Cl. It is one of the main industrial ores of the metal vanadium and a minor source of lead. A dense, brittle mineral, it is usually found in the form of red hexagonal crystals. It is an uncommon mineral, formed by the oxidation of lead ore deposits such as galena. First discovered in 1801 in Mexico, vanadinite deposits have since been unearthed in South America, Europe, Africa, and North America.
Proustite is a sulfosalt mineral consisting of silver sulfarsenide, Ag3AsS3, known also as ruby blende, light red silver, arsenic-silver blende or ruby silver ore, and an important source of the metal. It is closely allied to the corresponding sulfantimonide, pyrargyrite, from which it was distinguished by the chemical analyses of Joseph L. Proust (1754–1826) in 1804, after whom the mineral received its name.
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 173 °C (343 °F). Argentite is the stable form above that temperature. As argentite cools below that temperature its cubic form is distorted to the monoclinic form of acanthite. Below 173 °C acanthite forms directly. Acanthite is the only stable form in normal air temperature.
Realgar, also known as ″arsenic blende″, ″ruby sulphur″ or ″ruby of arsenic″, is an arsenic sulfide mineral with the chemical formula α-As4S4. It is a soft, sectile mineral occurring in monoclinic crystals, or in granular, compact, or powdery form, often in association with the related mineral, orpiment. It is orange-red in color, melts at 320 °C, and burns with a bluish flame releasing fumes of arsenic and sulfur. Realgar is soft with a Mohs hardness of 1.5 to 2 and has a specific gravity of 3.5. Its streak is orange colored. It is trimorphous with pararealgar and bonazziite.
Pyromorphite is a mineral species composed of lead chlorophosphate: Pb5(PO4)3Cl, sometimes occurring in sufficient abundance to be mined as an ore of lead. Crystals are common, and have the form of a hexagonal prism terminated by the basal planes, sometimes combined with narrow faces of a hexagonal pyramid. Crystals with a barrel-like curvature are not uncommon. Globular and reniform masses are also found. It is part of a series with two other minerals: mimetite (Pb5(AsO4)3Cl) and vanadinite (Pb5(VO4)3Cl), the resemblance in external characters is so close that, as a rule, it is only possible to distinguish between them by chemical tests. They were formerly confused under the names green lead ore and brown lead ore (German: Grünbleierz and Braunbleierz).
Tetrahedrite is a copper antimony sulfosalt mineral with formula: (Cu,Fe)
12Sb
4S
13. It is the antimony endmember of the continuous solid solution series with arsenic-bearing tennantite. Pure endmembers of the series are seldom if ever seen in nature. Of the two, the antimony rich phase is more common. Other elements also substitute in the structure, most notably iron and zinc, along with less common silver, mercury and lead. Bismuth also substitutes for the antimony site and bismuthian tetrahedrite or annivite is a recognized variety. The related, silver dominant, mineral species freibergite, although rare, is notable in that it can contain up to 18% silver.
Bournonite, also axotomous antimony glance, wheel ore, berthonite, volchite or dystomic glance (German: antimonbleikupferblende) is a sulfosalt mineral species, trithioantimoniate of lead and copper with the formula PbCuSbS3.
Stephanite is a silver antimony sulfosalt mineral with formula: Ag5SbS4. It is composed of 68.8% silver, and sometimes is of importance as an ore of this metal.
Sulfosalt minerals are sulfide minerals with the general formula AmBnXp, where
Miargyrite, formerly known as ruby blende or garnet blende is a mineral, a sulfide of silver and antimony with the formula AgSbS2. It is a dimorph of cuboargyrite. Originally discovered in the Freiberg district of Germany in 1824, it has subsequently been found in many places where silver is mined. It usually occurs in low temperature hydrothermal deposits. and forms black metallic crystals which may show a dark red internal reflection. The streak is also red.
Boulangerite or antimonbleiblende is an uncommon monoclinic orthorhombic sulfosalt mineral, lead antimony sulfide, formula Pb5Sb4S11. It was named in 1837 in honor of French mining engineer Charles Boulanger (1810–1849), and had been a valid species since pre-IMA. It was first described prior to 1959, and is now grandfathered.
Freieslebenite is a sulfosalt mineral composed of antimony, lead, and silver. Sulfosalt minerals are complex sulfide minerals with the formula: AmBnSp. The formula of freieslebenite is AgPbSbS3.
The silver antimonide mineral dyscrasite has the chemical formula Ag3Sb. It is an opaque, silver white, metallic mineral which crystallizes in the orthorhombic crystal system. It forms pyramidal crystals up to 5 cm (2.0 in) and can also form cylindrical and prismatic crystals.
Semseyite is a rarely occurring sulfosalt mineral and is part of the class of lead antimony sulfides. It crystallizes in the monoclinic system with the chemical composition Pb9Sb8S21. The mineral forms dark gray to black aggregates.
Native antimony is a mineral belonging to the group of native elements, with properties equivalent to those of the antimony element obtained by processing its ores. The name comes from the Latin antimonium. For centuries, the term antimony was also used to refer to stibnite or antimonite, the most common mineral containing this element, from which it was typically extracted. In mineralogy, the official name is simply antimony, although, as with other native elements, it is often referred to as native antimony to avoid ambiguity. It is unclear where native antimony was first discovered, although the Sala silver mine in Västmanland, Sweden, is considered the type locality.
Pearceite is one of the four so-called "ruby silvers", pearceite Cu(Ag,Cu)6Ag9As2S11, pyrargyrite Ag3SbS3, proustite Ag3AsS3 and miargyrite AgSbS2. It was discovered in 1896 and named after Dr Richard Pearce (1837–1927), a Cornish–American chemist and metallurgist from Denver, Colorado.
Parascorodite is a rare, secondary iron-arsenate mineral. It has a chemical formula of (FeAsO4·2H2O) and was discovered in 1967 using X-ray powder diffraction methods, when an unknown substance was found along with scorodite on medieval ore dumps in the Czech Republic. The holotype of parascorodite can be found in the mineralogical collection of the National Museum, Prague, Czech Republic under acquisition number P1p25/98.
Ruby blende or garnete blende are two close trivial names for several dissimilar minerals, with their appearance sometimes imitating red-colored precious stones, primarily natural garnets or rubies. In the scientific community, the systematic use of the term generally ended in the 19th century, with the transition to the modern system of naming minerals. Currently, both names are primarily used among mineral collectors and dealers, as well as geologists, miners and related trades.
Arsenic blende or Arsenblende is a trivial name that has partially fallen out of scientific use, used by mineralogists, as well as representatives of mining and craft professions in relation to at least two similar ore minerals — orpiment and realgar, in composition — arsenic sulfides.
This article incorporates text from a publication now in the public domain : Chisholm, Hugh, ed. (1911). "Pyrargyrite". Encyclopædia Britannica . Vol. 22 (11th ed.). Cambridge University Press. pp. 685–686.