RocksdayCuprite vs Pyrargyrite
The quickest way to tell Cuprite from Pyrargyrite: A fingernail scratches Pyrargyrite (Mohs 2.5) but not Cuprite (Mohs 3.5–4).
Copper oxide forming deep red cubes and octahedrons, sometimes as hair-like 'chalcotrichite'.
Photo: Didier Descouens, 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
- Fingernail: A fingernail scratches Pyrargyrite (Mohs 2.5) but not Cuprite (Mohs 3.5–4).
- Streak (rub on unglazed porcelain): Cuprite leaves a brownish red streak; Pyrargyrite leaves dark red.
Key differences
- Cuprite is cubic and its streak is brownish red.
Side by side
| Property | Cuprite | Pyrargyrite |
|---|---|---|
| Type | Mineral | Mineral |
| Mohs hardness | 3.5–4 | 2.5 |
| Luster | Adamantine to submetallic | Adamantine |
| Streak | Brownish red | Dark red |
| Colors | Red, Black | Red, Black |
| Crystal system | Cubic | Trigonal |
| Specific gravity | 6.1–6.15 | 5.8–5.9 |
| Formula | Cu₂O | Ag₃SbS₃ |
| Found in | Onganja, Namibia; Bisbee, Arizona | Freiberg, Germany; Guanajuato, Mexico |
Properties that are the same for both are grayed out.
How to identify cuprite
- Deep red, glinting crystals that can look almost black.
- Heavy.
- Brownish-red streak.
Crystal system: Cubic
Full Cuprite 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 cuprite and pyrargyrite?
Cuprite is a mineral (Cu₂O) with a Mohs hardness of 3.5–4 and an adamantine to submetallic luster, usually red or black. Pyrargyrite is a mineral (Ag₃SbS₃) with a Mohs hardness of 2.5 and an adamantine luster, usually red or black.
How can you tell cuprite from pyrargyrite?
A fingernail scratches Pyrargyrite (Mohs 2.5) but not Cuprite (Mohs 3.5–4). Cuprite leaves a brownish red streak; Pyrargyrite leaves dark red. Cuprite is cubic and its streak is brownish red.
Could you tell them apart from a blurry close-up?
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