Pyrargyrite

Pyrargyrite
Pyrargyrite
General
Category Sulfosalt
Chemical formula Ag3SbS3
Strunz classification 02.GA.05
Identification
Color dark red to red-black
Crystal habit Include prismatic crystals with rhombohedral and scalenohedral faces forming terminations. There is no perpendicular mirror plane and therefore a hemimorphic crystal can be seen, in some rare examples, with differing terminations at the top and bottom of the crystal. Typical crystals are poorly formed and modified heavily by secondary faces. Also found massive.
Crystal system trigonal; 3m
Cleavage Sometimes distinct in three directions forming rhombohedrons
Fracture conchoidal
Mohs scale hardness 2.5
Luster adamantine
Streak dark cherry red
Specific gravity approximately 5.8
Refractive index translucent to nearly opaque
Other characteristics darkens upon exposure to light; crystals are frequently striated

Pyrargyrite is a sulfosalt mineral consisting of silver sulfantimonide, 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 sulfarsenide known as proustite or light red silver ore. Ruby silver or red silver ore (German Rotgiiltigerz) 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, &c. The best crystallized specimens are from Sankt Andreasberg in the Harz, Freiberg in Saxony, and Guanajuato in Mexico. 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.

Pyrargyrite silver ore from the Comstock Lode, Storey Co., Nevada, USA

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.

References

 This article incorporates text from a publication now in the public domainChisholm, Hugh, ed (1911). Encyclopædia Britannica (11th ed.). Cambridge University Press. 


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  • PYRARGYRITE — Appelée aussi «argent rouge» antimonié ou argyrythrose, la pyrargyrite est un sulfoantimoniure d’argent qui possède un système cristallin rhomboédrique hémimorphe. Les individus sont souvent prismatiques. Les formes bipyramidées par macles… …   Encyclopédie Universelle

  • Pyrargyrite — Pyrargyrite[1] Catégorie II : sulfures et sulfosels[2] …   Wikipédia en Français

  • Pyrargyrite — Py*rar gy*rite, n. [Gr. ? fire + ? silver.] (Min.) Ruby silver; dark red silver ore. It is a sulphide of antimony and silver, occurring in rhombohedral crystals or massive, and is of a dark red or black color with a metallic adamantine luster.… …   The Collaborative International Dictionary of English

  • pyrargyrite — [pī rär′ji rīt΄] n. [Ger pyrargyrit < Gr pyr, FIRE + argyros, silver + Ger it, ITE1] a dark colored, rhombohedral mineral, Ag3SbS3, an ore of silver; silver antimony sulfide …   English World dictionary

  • pyrargyrite — Red Red, a. [Compar. {Redder} ( d?r); superl. {Reddest}.] [OE. red, reed, AS. re[ a]d, re[ o]d; akin to OS. r[=o]d, OFries. r[=a]d, D. rood, G. roht, rot, OHG. r[=o]t, Dan. & Sw. r[ o]d, Icel. rau[eth]r, rj[=o][eth]r, Goth. r[ a]uds, W. rhudd,… …   The Collaborative International Dictionary of English

  • pyrargyrite — pirargiritas statusas T sritis chemija apibrėžtis Mineralas. formulė Ag₃SbS₃ atitikmenys: angl. pyrargyrite rus. пираргирит …   Chemijos terminų aiškinamasis žodynas

  • pyrargyrite — pīˈrärjəˌrīt, pə̇ˈr noun ( s) Etymology: German pyrargyrit, from pyr + argyr + it ite : a silver antimony sulfide Ag3SbS3 that is isomorphous with proustite, occurs in rhombohedral crystals or massive, and has a dark red or black color with a… …   Useful english dictionary

  • pyrargyrite — /puy rahr jeuh ruyt /, n. a blackish mineral, silver antimony sulfide, AgSbS3, showing, when transparent, a deep ruby red color by transmitted light; ruby silver: an ore of silver. [1840 50; PYR + Gk árgyr(on) silver + ITE1] * * * ▪ mineral… …   Universalium

  • pyrargyrite — noun Ruby silver; dark red silver ore. It is a sulphide of antimony and silver, AgSbS, occurring in rhombohedral crystals or massive, and is of a dark red or black color with a metallic adamantine luster; it is an important silver ore …   Wiktionary

  • pyrargyrite — pyr·ar·gy·rite …   English syllables

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