Acanthite
| Colour | Black, Gray |
|---|---|
| Mohs hardness | 2.0–2.5 |
| Lustre | Metallic |
| Streak | Black |
| Crystal system | Monoclinic |
| Transparency | Opaque |
| Cleavage | Indistinct |
| Fracture | Uneven |
| Chemical formula | Ag 2 S |
| Specific gravity | 7.20–7.22 |
What is Acanthite?
Acanthite is a form of silver sulfide with the chemical formula Ag2S. It crystallizes in the monoclinic system and is the stable form of silver sulfide below 173 °C (343 °F). Argentite is the stable form above that temperature. As argentite cools below that temperature its cubic form is distorted to the monoclinic form of acanthite. Below 173 °C acanthite forms directly. Acanthite is the only stable form in normal air temperature.
How to identify Acanthite
- Lustre: Metallic.
- Hardness: Mohs 2.0–2.5 — soft; a knife will scratch it.
- Streak: Black.
- Habit: Monoclinic crystal system.
Acanthite in different forms
Stones often confused with Acanthite
Frequently asked questions
How hard is Acanthite?
Acanthite is Mohs 2.0–2.5 on the hardness scale.
What colour is Acanthite?
Acanthite is typically black, gray (Iron-black).