RocksdayProustite vs Pyrargyrite
The quickest way to tell Proustite from Pyrargyrite: Proustite leaves a scarlet streak; Pyrargyrite leaves dark red.
A translucent scarlet silver sulfosalt that darkens when exposed to light.
Photo: Robert M. Lavinsky, CC BY-SA 3.0
Dark ruby silver, the antimony partner of proustite. Deep red crystals that darken in the light.
Photo: Robert M. Lavinsky, CC BY-SA 3.0
Quick tests
- Streak (rub on unglazed porcelain): Proustite leaves a scarlet streak; Pyrargyrite leaves dark red.
Key differences
- Pyrargyrite is darker red and is the antimony version, not the arsenic one.
- Proustite is lighter scarlet and is the arsenic version, Ag₃AsS₃.
Side by side
| Property | Proustite | Pyrargyrite |
|---|---|---|
| Type | Mineral | Mineral |
| Mohs hardness | 2–2.5 | 2.5 |
| Luster | Adamantine | Adamantine |
| Streak | Scarlet | Dark red |
| Colors | Red | Red, Black |
| Crystal system | Trigonal | Trigonal |
| Specific gravity | 5.55–5.64 | 5.8–5.9 |
| Formula | Ag₃AsS₃ | Ag₃SbS₃ |
| Found in | Chañarcillo, Chile; Freiberg, Germany | Freiberg, Germany; Guanajuato, Mexico |
Properties that are the same for both are grayed out.
How to identify proustite
- Translucent scarlet crystals with a brilliant luster.
- Darkens to gray in light.
- Scarlet streak.
Crystal system: Trigonal
Full Proustite guide →How to identify pyrargyrite
- Dark crimson to nearly black, with a brilliant luster.
- Dark red streak — darker than proustite's scarlet.
- Soft (2.5) and very heavy. Turns gray if left in strong light.
Crystal system: Trigonal
Full Pyrargyrite guide →More comparisons
Frequently asked questions
What is the difference between proustite and pyrargyrite?
Proustite is a mineral (Ag₃AsS₃) with a Mohs hardness of 2–2.5 and an adamantine luster, usually red. Pyrargyrite is a mineral (Ag₃SbS₃) with a Mohs hardness of 2.5 and an adamantine luster, usually red or black.
How can you tell proustite from pyrargyrite?
Proustite leaves a scarlet streak; Pyrargyrite leaves dark red. Pyrargyrite is darker red and is the antimony version, not the arsenic one. Proustite is lighter scarlet and is the arsenic version, Ag₃AsS₃.
Could you tell them apart from a blurry close-up?
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