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Proustite

Crystal system · Trigonal

Proustite is a sulfosalt mineral recognized among collectors for its crystal form and distribution, with notable Chinese occurrences.

About Proustiteextended article

Care notesLight-sensitive (darkens). Store in dark, low humidity. Full cleaning guide →
Market availability: Rare
Sought after; limited supply. Major shows and specialist dealers only.
Crystal system
Trigonal

Proustite — “light ruby silver” — is a silver-arsenic sulfosalt celebrated for its translucent ruby-red to scarlet color. Together with pyrargyrite (“dark ruby silver”), it forms one of the most beautiful and historically important silver-mineral pairs.

Occurrence

Classic localities: Chañarcillo (Chile) — among the finest 19th-century specimens; Sainte-Marie-aux-Mines (France); Schneeberg (Germany); Cobalt (Ontario). Proustite remains scarce in Chinese deposits.

Identification

Translucent scarlet-red prismatic trigonal crystals + adamantine luster + softness. Distinguish from pyrargyrite (darker, deeper red bordering on black-red) by lighter color when held to strong light. WARNING: proustite is light-sensitive — fine crystals must be stored in darkness or they tarnish to dull black.

Collector Notes

Top-grade Chañarcillo proustite crystals are among the most valuable historical silver minerals — six-figure prices for the best pieces. Always store away from sunlight.

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External research links for Proustite
Published: May 6, 2026 · Last reviewed: May 6, 2026
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About Proustite

Proustite is a sulfosalt mineral in the proustite group and has the chemical formula Ag3AsS3. It crystallizes in the trigonal system and is relatively soft, requiring careful handling. Its combination of structural character and global distribution make it a recognized species in both systematic and aesthetic collections.

Identification & care

Proustite typically forms prismatic, rhombohedral, scalenohedral crystals; massive; granular. Its color is typically scarlet, vermilion red and cinnabar red (darkens irreversibly on light exposure). The luster is adamantine, sub-metallic, the streak is red, and specimens range from transparent to translucent (when fresh, darkens). The cleavage is distinct on {10-11}. The fracture is conchoidal to uneven, which aids identification.

Collector context

How it forms

In terms of geology, Proustite forms in low-temperature hydrothermal silver veins; typically in the upper silver zone associated with other silver minerals. It is commonly found in association with pyrargyrite, native silver, argentite/acanthite, galena, calcite, dolomite.

Classic Chinese localities

Documented Chinese occurrences are recorded at Shizhuyuan Mine, among others.

Why collectors care

Collectors pursue Proustite for the clarity of its crystal form and, in good material, saturated color that reads instantly across a display case. A well-terminated proustite on clean matrix photographs well, identifies quickly, and anchors a cabinet piece. Top Chinese specimens over the last two decades have reset the bar for what proustite looks like at collector grade.

What affects value

Value in Proustite is assessed, in typical order of weight, against: (1) locality provenance; (2) size relative to the species norm; (3) crystal form and termination sharpness; (4) color saturation and zoning; (5) transparency and internal clarity; (6) matrix quality and aesthetic balance; (7) condition (absence of damage, chips, or repair). Cleaning quality and verified locality documentation act as multipliers across the above.

Naming history

The name Proustite has a specific etymological and historical context — see Mindat's reference entry for provenance details. We have retained naming data at the record level; published prose is paraphrased from factual fields rather than copied from source.