• Chemistry: Ag3AsS3, Silver Arsenic Sulfide
  • Class: Sulfides
  • Subclass: Sulfosalts
  • Uses: A minor ore of silver, as mineral specimens and as a rare gemstone.
  • Specimens

Proustite is one of only an few sulfides that are not metallic or opaque. In fact it is at times cut for gemstones, although it is far too soft to wear in everyday jewelry. Its color is a bright scarlet red to reddish orange and is distinctive. The nickname "Ruby Silver" has been applied to proustite as well as the closely related mineral pyrargyrite.

Pyrargyrite is a silver antimony sulfide and is isostructural with proustite. Isostructural means that the two minerals have the same structure but a different chemistry. There is some substitution of the antimony and arsenic. But in both minerals, the substitution is minor and no solid solution is believed to exist between the two minerals.

Proustite is the rarer of the two minerals and is usually found in the same ore veins with pyrargyrite, silver and other silver sulfides. Fine crystals, with their transparency, luster and color, are very attractive mineral specimens. However, as with other silver minerals, it is reactive to light and can form a white coating upon exposure. This coating can be wiped off, but fine specimens should be stored in closed containers with exposure to light limited.


  • Color is a bright scarlet red to reddish orange.
  • Luster is adamantine.
  • Transparency: Crystals are translucent to transparent.
  • Crystal System is trigonal; 3 m
  • Crystal Habits: 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. Also found massive.
  • Cleavage is sometimes distinct in three directions forming rhombohedrons.
  • Fracture is conchoidal.
  • Hardness is 2 - 2.5
  • Specific Gravity is approximately 5.6 (very heavy for translucent minerals)
  • Streak is red.
  • Associated Minerals include pyrargyrite, silver, tetrahedrite, calcite, quartz, galena, sphalerite and other silver vein minerals.
  • Other Characteristics: A white film forms on the surface of crystals upon exposure to light.
  • Notable Occurrences include Atacama, Chile; silver mines in Saxony Germany; Poorman Mine, Idaho and Chihuahua, Mexico.
  • Best Field Indicators are crystal habit, density, association with pyrargyrite and color.
PROUSTITE specimens:
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PROUSTITE specimen pro-1
$ 27.00
Dims: 2.4 x 1.5 x 1.0" (6.1 x 3.8 x 2.5 cm)
Wt: 3.2 oz. (92 g)
Bulldog Mine, Creede, Mineral County, Colorado, U.S.A.
A small vein of semicrystalline Proustite extends into the metallic sulfide base of this specimen. This vein shows no definite crystal form, but any crystals would not exceed a few millimeters in diameter, so I cannot be sure. The Proustite has a deep red color and a pearly luster, and though it is transparent, it is rather hard to see against the dark gray base. The base rock itself is made up of a variety of sulfides that appear to include pyrite and/or chalcopyrite, tetrahedrite and/or galena, or a combination of any or all of these.
no photo
pro-1 ($ 27.00)
Bulldog Mine, Creede, Mineral County, Colorado, U.S.A.
PROUSTITE specimen pro-2
$ 36.00
Dims: 0.3 x 0.2 x 0.2" (7 x 5 x 5 mm)
Wt: 0.3 oz. (9 g) w/ specimen box
Aue, Saxony, Germany
This Proustite specimen is very small, bordering on a micromount. It consists of a cluster of tiny Proustite crystals that appear to be in good condition (some obvious damage is present) and do not exceed 2 mm in length, width, or thickness. These crystals show a rather heavily warped hexagonal form due to intergrowth and have the deep red color and submetallic luster that is common for this specie. Another mineral also appears to be present, with a brighter metallic luster and a silvery-yellow color. According to the documentation, this other mineral is Sternbergite, a silver iron sulfide. There is no host rock present, and the piece is affixed inside a plastic thumbnail box.
no photo
pro-2 ($ 36.00)
Aue, Saxony, Germany
PROUSTITE specimen pro-3
$ 72.00
Dims:1.6x0.9x0.9" (4.1x2.3x2.3 cm)
Wt: 0.8oz. (23g)
Song co., Henan prov., China
This specimen consists of dozens of minute crystals of proustite scattered throughout the matrix with flecks of native silver. This association is not surprising, considering that proustite is a silver arsenic sulfide. The crystals on this specimen are too small to study, even with a loupe. Proustite is named for the French chemist, J. Proust.
no photo
pro-3 ($ 72.00)
Song co., Henan prov., China
PROUSTITE specimen pro-4
$ 80.00
Dims:1.5x1.2x1.0" (3.8x3.0x2.5 cm)
Wt: 1.2oz. (34g)
Song co., Henan prov., China
Dozens of tiny crystals of proustite and flecks of native silver are interspersed throughout the matrix of the host material on this specimen. The crystals are far to small to study, even with a loupe.
no photo
pro-4 ($ 80.00)
Song co., Henan prov., China
PROUSTITE specimen pro-5
$ 65.00
Dims: 1.8x1.8x1.4" (4.5x4.5x3.5 cm)
Wt: 1.88 oz. (53.2g)
Imiter Deposit, Saghro Oriental, Anti-Atlas, Morocco
This specimen has some excellent proustite crystals resting on a host rock that appears to be a mixture of quartzite and several metal sulfides, almost certainly including tennantite and cobaltite. Under a loupe, many tiny areas are brightly irridescent, and a multitude of crystal shapes indicates that many different minerals are present. The best crystals are clearly the proustites, which are transparent, deep red, and have a vitreous luster. The largest of these is only a few millimeters long, but there are hundreds, scattered over (and through) the host rock.
no photo
pro-5 ($ 65.00)
Imiter Deposit, Saghro Oriental, Anti-Atlas, Morocco
PROUSTITE specimen pro-7
$ 60.00
Dims: 1.50x1.18x0.98" (3.8x3.0x2.5cm)
Wt: 0.96oz. (27.3g)
Imiter silver mine, Morocco
Maroon, lustrous crystals of proustite adorn the gray surface of this specimen. The proustite crystals are translucent (nearly transparent), prismatic crystals with shallow pyramidal terminations. There are crystals on nearly all sides of the specimen. One image shows the multitude of crystals on one face, while the other shows the largest crystals (on the opposite face).
no photo
pro-7 ($ 60.00)
Imiter silver mine, Morocco
PROUSTITE specimen pro-6
$ 35.00
Dims: 1.30x0.75x0.51" (3.3x1.9x1.3cm)
Wt: 0.52oz (14.7g)
Imiter silver mine, Morocco
This porous gray rock is host to hundreds of tiny proustite crystals - indeed, they are scattered on every surface and permiate the pores of the rock. The proustite crystals are a deep maroon color, nearly transparent, and have deep striations along the length of the prisms. In a few areas, the proustite has darkened towards black, but most of the crystals are fresh and red (very little darkening from exposure to light).
no photo
pro-6 ($ 35.00)
Imiter silver mine, Morocco


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