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The Mineral pyrargyrite

Red Prismatic Pyrargyrite Crystals

Pyrargyrite is an interesting mineral that contains silver in its chemical structure. It is one of the few silver-bearing minerals that can exhibit transparency. Pyrargyrite contains two very distinct habits: as transparent, deep-red crystals, and in opaque, dark-metallic gray form. Many of the opaque and metallic-looking specimens will still exhibit slight transparency and red color when backlit.

Pyrargyrite is light sensitive. Prolonged exposure to bright light will darken its transparency and cause it to become darker. Exposure also may cause a dark, dull film to form on crystal faces; this film can be removed by brushing a specimen with soap and water.

Pyrargyrite is very similar to Proustite, and forms a series with it. Pyrargyrite is the antimony-rich member, and Proustite is the arsenic-rich member. It is often not possible to visually distinguish these two minerals from each other. Pyrargyrite is the more common of this series, although good crystals of both these minerals are difficult to come across. Most good material in collections today are from closed, historical localities.

Pyrargyrite is named from the Greek words Pyr, "Fire" in allusion to the color of this mineral, and Argyros, meaning silver, describing its silver content.

Chemical Formula

Ag3SbS3

Color

Dark red, dark purplish-red, dark metallic-gray, black

Crystal System

Hexagonal

Properties

Streak
Purplish Red
Hardness
2.5
Transparency
Transparent to opaque
Specific Gravity
5.8 - 5.9
Luster
Adamantine, submetallic, metallic
Cleavage
3,1
Fracture
Conchoidal to uneven
Tenacity
Brittle

Crystal Habits

In prismatic crystals, often as complex scalenohedral crystals that are truncated at the tip. Crystals are typically hemimorphic, with one crystal termination larger than the other, though this habit is rarely observed due to rarity of doubly terminated crystals. Also in blocky groups of stubby crystals, grainy, encrusting, dendritic, and massive. Crystals are usually striated horizontally on an angle, and may have complex growths and angles.

3D Crystal Atlas

Additional Information

Composition
Silver antimony sulfide, sometimes with some arsenic
In Group
Sulfides; Sulfosalts
Striking Features
Color, habits, and mode of occurrence
Environment
Low temperature epithermal veins in silver ore deposits.
Rock Type
Sedimentary, Metamorphic

Other Names

Dark Red Silver Ore
Dark Ruby Silver Ore
Red Silver Ore
Ruby Silver Describing any silver-bearing sulfosalt that can form in a deep red color. The term specifically refers to Pyrargyrite and Proustite, but may also refer to Polybasite and Pearceite.

Uses

Pyrargyrite was used as an ore of silver, but today is a highly valuable rare collector's mineral, especially when in red color and transparent.

Noteworthy Localities

Pyrargyrite is noted from many of the classic silver-producing localities in Western Europe and Latin America. Gemany contains several classic localities in Saxony, where outstanding Pyrargyrite was found in sharp, well-formed crystals. Localities there include the St Andreasberg District, Harz Mountains; the Freiberg District, Erzgebirge; and the Schlema and Schneeberg Districts, Erzgebirge.

Other classic European Pyrargyrite localities include Jáchymov, Krušné Hory Mts, Bohemia, Czech Republic; Příbram, Bohemia, Czech Republic; and Hiendelaencina, Guadalajara, Spain.

Important South American localities for Pyrargyrite are the Uchucchacua Mine, Oyon, Lima Department, Peru; the San Genaro Mine, Castrovirreyna, Huancavelica Department, Peru; Porco and Colquechaca, Potosí Department, Bolivia; and Chañarcillo, Copiapó Province, Atacama Desert, Chile.

In Mexico, lustrous, complex crystals have come from Fresnillo, Zacatecas; and large crystals clusters from the San Juan de Rayas Mine, Guanajuato. Pyrargyrite is very rare in U.S., with few localities producing any specimens of note, though small microcrystals occur at the Advance Mine, Colorado Hill, Alpine Co., California.

Common Mineral Associations

Quartz, Calcite, Silver, Tetrahedrite, Acanthite, Galena, Sphalerite

Distingushing Similar Minerals

Proustite - Often has a redder color than Pyrargyrite; otherwise indistinguishable without complex analysis.
Cuprite,  Sphalerite, and Rutile - Form in different crystal types, have greater hardness.

pyrargyrite Photos



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