RocksdayAcanthite vs Chalcocite
How to tell them apart
Silver sulfide and the most important silver ore — a soft, black, sectile mineral.
Photo: Ivar Leidus, CC BY-SA 4.0
A dark gray copper sulfide and one of the richest copper ores.
Photo: Didier Descouens, CC BY-SA 3.0
Quick tests
- Streak (rub on unglazed porcelain): Acanthite leaves a black streak; Chalcocite leaves dark gray.
Key differences
- Chalcocite is lighter.
- Acanthite is heavier and also sectile; a lab test may be needed.
Side by side
| Property | Acanthite | Chalcocite |
|---|---|---|
| Type | Mineral | Mineral |
| Mohs hardness | 2–2.5 | 2.5–3 |
| Luster | Metallic | Metallic |
| Streak | Black | Dark gray |
| Colors | Black, Gray | Gray, Black |
| Crystal system | Monoclinic | Monoclinic |
| Specific gravity | 7.2–7.4 | 5.5–5.8 |
| Formula | Ag₂S | Cu₂S |
| Found in | Guanajuato, Mexico; Freiberg, Germany | Bristol, Connecticut; Cornwall, England |
Properties that are the same for both are grayed out.
How to identify acanthite
- Black to lead-gray, dull metallic.
- Cuts like lead with a knife.
- Very heavy.
Crystal system: Monoclinic
Full Acanthite guide →How to identify chalcocite
- Dark lead-gray, dulling to black.
- Soft and sectile — a knife shaves it.
- Heavy.
Crystal system: Monoclinic
Full Chalcocite guide →More comparisons
Could you tell them apart from a blurry close-up?
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