RocksdayActinolite vs Epidote
How to tell them apart
A green amphibole forming radiating sprays of long crystals in greenschist rocks.
Photo: Didier Descouens, CC BY-SA 4.0
A pistachio-green metamorphic mineral. Mixed with pink feldspar it forms the popular stone 'unakite'.
Photo: Gleb Korovko, CC BY 4.0
Quick tests
- Streak (rub on unglazed porcelain): Actinolite leaves a white streak; Epidote leaves gray to white.
Key differences
- Epidote is a yellowish pistachio green with one cleavage.
Side by side
| Property | Actinolite | Epidote |
|---|---|---|
| Type | Mineral | Mineral |
| Mohs hardness | 5–6 | 6–7 |
| Luster | Vitreous to silky | Vitreous |
| Streak | White | Gray to white |
| Colors | Green, Gray, Black | Green, Black |
| Crystal system | Monoclinic | Monoclinic |
| Specific gravity | 3–3.2 | 3.3–3.6 |
| Formula | Ca₂(Mg,Fe)₅Si₈O₂₂(OH)₂ | Ca₂(Al₂Fe)(SiO₄)(Si₂O₇)O(OH) |
| Found in | Zillertal, Austria; Vermont | Prince of Wales Island, Alaska; Knappenwand, Austria |
Properties that are the same for both are grayed out.
How to identify actinolite
- Bright to dark green needles or blades.
- Often radiating like a star.
- Two amphibole cleavages.
Crystal system: Monoclinic
Full Actinolite guide →How to identify epidote
- Distinctive pistachio to dark green.
- Striated prisms.
- Hardness 6–7.
- Commonly fills cracks in altered rocks.
Crystal system: Monoclinic
Full Epidote guide →More comparisons
Could you tell them apart from a blurry close-up?
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