Proustite is a highly prized silver sulfosalt known for its intense, ruby-red color and adamantine luster. It is light-sensitive and will darken or develop a crust if exposed to strong light over time, so it should be stored in a dark, cool container. Look for it as beautiful, sharp trigonal crystals in low-temperature hydrothermal silver deposits.
Is this proustite?
5-step field checkRun through these checks against the specimen in your hand. The more boxes tick, the more confident the ID.
- 1Test the hardnessTry to scratch proustite with a known reference. Proustite sits at Mohs 2-2.5, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: vermilion.
- 3Read the lusterHold the specimen under a strong light. Luster: adamantine.
- 4Match the color rangeCompare against the expected color range: scarlet-red, vermilion, reddish gray.
- 5Look at form & habitCrystal system: trigonal. Typical habit: blocky, crystalline, massive.
Often confused with
Proustite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Proustite leaves vermilion, Pyrargyrite leaves purplish red.
How to tell apart: Streak differs, so Proustite leaves vermilion, Cinnabar leaves scarlet.
How to tell apart: Streak differs, so Proustite leaves vermilion, Realgar leaves red-orange to red; luster reads adamantine on Proustite and resinous to greasy on Realgar.
Often found alongside proustite
Minerals reported to co-occur with proustite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Ag₃AsS₃
- Mohs hardness
- 2-2.5
- Density
- 5.57 g/cm³
- Colors
- Streak
- Vermilion
- Luster
- Adamantine
- Transparency
- Translucent, darkens with exposure to light
- Crystal system
- Trigonal
- Crystal habit
- Blocky, crystalline, massive
- Cleavage
- Distinct on {1011}
- Rarity
- Rare
- Uses
- Collector, Minor silver ore
- Host rock
- A late-forming mineral in hydrothermal deposits, in the oxidized and enriched zone, associated with other silver minerals and sulfides
Where rockhounds find proustite
Classic worldwide localities
- Red Mountain, San Juan Co., and at Georgetown, Clear Creek Co., Colorado, USA
- Poorman mine, Silver City district, Owyhee Co., Idaho, USA
- Star mine, Cherry Creek district, White Pine Co., Nevada, USA
- Himmelsfürst mine, Erbisdorf, near Freiberg, Germany
- Niederschlema, Saxony, Germany
- Săcărı̂mb (Nagyág), Romania
Field-hunting tip
Where it forms: A late-forming mineral in hydrothermal deposits, in the oxidized and enriched zone, associated with other silver minerals and sulfides. If you start seeing silver, arsenic, xanthoconite in float, you are in the right ground. Typical habit: blocky, crystalline, massive. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify proustite?+
Where is proustite found?+
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What rocks look like proustite?+
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Find proustite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
