RocksdayPrehnite vs Wavellite
How to tell them apart
A pale green silicate that forms bubbly, translucent crusts, often with black epidote needles.
Photo: Ivar Leidus, CC BY-SA 4.0
An aluminum phosphate that forms green radiating discs, like pinwheels, on rock fractures.
Photo: Didier Descouens, CC BY-SA 3.0
Quick tests
- Scratch glass: Prehnite scratches glass (Mohs 6–6.5); Wavellite can't (Mohs 3.5–4).
Key differences
- Prehnite forms bubbly crusts and is harder.
Side by side
| Property | Prehnite | Wavellite |
|---|---|---|
| Type | Mineral | Mineral |
| Mohs hardness | 6–6.5 | 3.5–4 |
| Luster | Vitreous to pearly | Vitreous to pearly |
| Streak | White | White |
| Colors | Green, Yellow, White | Green, Yellow, White |
| Crystal system | Orthorhombic | Orthorhombic |
| Specific gravity | 2.8–2.95 | 2.36 |
| Formula | Ca₂Al(AlSi₃O₁₀)(OH)₂ | Al₃(PO₄)₂(OH,F)₃·5H₂O |
| Found in | Wave Hill, Australia; Kayes, Mali | Mauldin Mountain, Arkansas; Devon, England |
Properties that are the same for both are grayed out.
How to identify prehnite
- Pale apple-green to yellowish, translucent.
- Bubbly, rounded crusts or bow-tie aggregates.
- Hardness about 6.
Crystal system: Orthorhombic
Full Prehnite guide →How to identify wavellite
- Flat green 'pinwheel' circles on rock surfaces.
- Radiating needle-like fibers.
- Hardness about 4.
Crystal system: Orthorhombic
Full Wavellite guide →More comparisons
Could you tell them apart from a blurry close-up?
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