Proustite

Big Photo

Chile
.35 carats
© raregemhunter

Proustite is named after Joseph L. Proust, French chemist.

Proustite forms beautiful prismatic transparent adamantine dark red crystals, but they become dull black and opaque on exposure to light, therefore they must be kept in darkness.

Proustite is a rare stone. It is cut into brilliant faceted stones, but they are too soft to be set in jewelry.

Proustite Gemstones by Colour

This table shows the variety of hues this gemstone can be found in. Click on a photo for more information.
 

Proustite Gemstones by Size

This table shows distribution of Proustite gemstone sizes that are listed on this site. This can give a good indication as to the general availability of this gemstone in different sizes.
Contributed photos
Lightest:.35 cts
Heaviest:12.27 cts
Average:6.40 cts
Total photos:3
Do you have a larger Proustite? Why not upload a photo?
0.35ct to 1.54ct1.54ct to 2.73ct2.73ct to 3.93ct3.93ct to 5.12ct5.12ct to 6.31ct6.31ct to 7.50ct7.50ct to 8.69ct8.69ct to 9.89ct9.89ct to 11.08ct11.08ct to 12.27ct
General Information
Chemical Formula
Ag
 
3
AsS
 
3
Michael O’Donoghue, Gems, Sixth Edition (2006)
More from other references
Photos of natural/un-cut material from mindat.org
Physical Properties of Proustite
Mohs Hardness2.5
Ulrich Henn and Claudio C. Milisenda, Gemmological Tables (2004)
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Specific Gravity5.51 to 5.64
Ulrich Henn and Claudio C. Milisenda, Gemmological Tables (2004)
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TenacityBrittle
Arthur Thomas, Gemstones (2009)
Cleavage QualityDistinct
Arthur Thomas, Gemstones (2009)
FractureUneven,Conchoidal
Arthur Thomas, Gemstones (2009)
Light SensitivityOften darkens with exposure to light
Michael O’Donoghue, Gems, Sixth Edition (2006)
Optical Properties of Proustite
Refractive Index2.792 to 3.087
Ulrich Henn and Claudio C. Milisenda, Gemmological Tables (2004)
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Optical CharacterUniaxial/-
Ulrich Henn and Claudio C. Milisenda, Gemmological Tables (2004)
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Birefringence0.295
Ulrich Henn and Claudio C. Milisenda, Gemmological Tables (2004)
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PleochroismStrong
Arthur Thomas, Gemstones (2009)
DispersionWeak
Arthur Thomas, Gemstones (2009)
Colour
Colour (General)Cinnabar to scarlet-red
Walter Schumann, Gemstones of the world (2001)
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TransparencyOpaque
Ulrich Henn and Claudio C. Milisenda, Gemmological Tables (2004) Rarely transparentMore from other references
LustreAdamantine
Michael O’Donoghue, Gems, Sixth Edition (2006)
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Crystallography of Proustite
Crystal SystemTrigonal
Ulrich Henn and Claudio C. Milisenda, Gemmological Tables (2004)
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HabitRhombohedral, prismatic
Michael O’Donoghue, Gems, Sixth Edition (2006)
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Geological Environment
Where found:Proustite occurs as a late-forming mineral in hydrothermal deposits in the oxidized and enriched zone, with other silver minerals and sulphides.
Michael O’Donoghue, Gems, Sixth Edition (2006)
Further Information
Mineral information:Proustite information at mindat.org
Significant Gem Localities
Chile
 
  • Atacama
    • Copiapó Province
      • Chañarcillo
Gems, Sixth Edition, Michael O’Donoghue, 2006, p. 440
Peru
 
  • Lima
    • Oyon Province
Copyright © Jolyon & Katya Ralph 1993-2019. Site Map. Locality, gem & photograph data are the copyright of the individuals who submitted them. For more information please contact the . Gemdat.org is an online information resource dedicated to providing free gemmological information to all.