RocksdayEpidote vs Zoisite
How to tell them apart
A pistachio-green metamorphic mineral. Mixed with pink feldspar it forms the popular stone 'unakite'.
Photo: Gleb Korovko, CC BY 4.0
A calcium aluminum silicate best known as green rock studded with red ruby crystals.
Photo: Robert M. Lavinsky, CC BY-SA 3.0
Quick tests
- Streak (rub on unglazed porcelain): Epidote leaves a gray to white streak; Zoisite leaves white.
Key differences
- Epidote is darker pistachio green.
Side by side
| Property | Epidote | Zoisite |
|---|---|---|
| Type | Mineral | Mineral |
| Mohs hardness | 6–7 | 6–7 |
| Luster | Vitreous | Vitreous |
| Streak | Gray to white | White |
| Colors | Green, Black | Green, Pink, Gray |
| Crystal system | Monoclinic | Orthorhombic |
| Specific gravity | 3.3–3.6 | 3.15–3.38 |
| Formula | Ca₂(Al₂Fe)(SiO₄)(Si₂O₇)O(OH) | Ca₂Al₃(SiO₄)(Si₂O₇)O(OH) |
| Found in | Prince of Wales Island, Alaska; Knappenwand, Austria | Longido, Tanzania; Norway |
Properties that are the same for both are grayed out.
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 →How to identify zoisite
- Green massive stone, often with red ruby and black hornblende.
- Pink variety (thulite) is opaque.
- Hardness about 6.5.
Crystal system: Orthorhombic
Full Zoisite guide →More comparisons
Could you tell them apart from a blurry close-up?
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