RocksdayAnalcime vs Leucite
How to tell them apart
A zeolite forming glassy 24-faced crystals in basalt cavities.
Photo: Ivar Leidus, CC BY-SA 4.0
A potassium silicate forming white, ball-like 24-faced crystals in some lavas.
Photo: Dave Dyet http://www.shutterstone.com http://www.dyet.com, Public domain
Key differences
- Leucite is embedded in lava, not in open cavities.
- Analcime looks almost identical but grows in cavities, not embedded in lava.
Side by side
| Property | Analcime | Leucite |
|---|---|---|
| Type | Mineral | Mineral |
| Mohs hardness | 5–5.5 | 5.5–6 |
| Luster | Vitreous | Vitreous |
| Streak | White | White |
| Colors | Clear, White, Pink | White, Gray |
| Crystal system | Cubic | Tetragonal (pseudo-cubic) |
| Specific gravity | 2.24–2.29 | 2.45–2.5 |
| Formula | NaAlSi₂O₆·H₂O | KAlSi₂O₆ |
| Found in | Cyclopean Isles, Sicily; Mont Saint-Hilaire, Quebec | Mount Vesuvius, Italy; Alban Hills, Italy |
Properties that are the same for both are grayed out.
How to identify analcime
- Clear to white trapezohedra (ball-like, 24 faces).
- In cavities of basalt with other zeolites.
- Hardness about 5.
Crystal system: Cubic
Full Analcime guide →How to identify leucite
- Dull white rounded crystals with many faces, set in lava.
- Hardness about 6.
- Light in weight.
Crystal system: Tetragonal (pseudo-cubic)
Full Leucite guide →More comparisons
Could you tell them apart from a blurry close-up?
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