By Parent Géry (Own work) [CC-BY-SA-3.0], via Wikimedia Commons
Leucite is abundant in various lava rocks but is extremely rare in facetable crystals. The material has little appeal except for its extreme scarcity. Stones often have a slight milky or cloudy look, and anything over 3 carats is likely to be included.
Leucite Value
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Leucite Information
| Data | Value |
| Name | Leucite |
| Crystallography | Tetragonal (pseudo-cubic). Crystals trapezohedral; granular. |
| Colors | Colorless, white, gray, yellowish. |
| Luster | Vitreous; dull on some crystals. |
| Hardness | 5.5-6. |
| Density | 2.47-2.50. |
| Birefringence | Low to zero. |
| Cleavage | Poor. Fracture conchoidal. Brittle. |
| Stone Sizes | Italian material has been cut to about 3 carats. There is very little of this material, always small, and clean only in very tiny stones. |
| Luminescence | Medium-bright orange in LW (Italy) or none. Bluish glow in X-rays. |
| Formula | KAISi2O6. |
Optics: Isotropic; N – 1.50.
Optically (+) if uniaxial.
Occurrence: in potassium-rich basic lavas. Wyoming: Montana: Arkansas: New Jersey.
British Columbia: France; Germany: Zaire: Uganda; Australia.
Alban Hills, near Rome, Italy: source of the world’s only transparent leucite crystals. These are colorless, up to about 1 cm.
Comments: Leucite is abundant in various lava rocks but is extremely rare in facetable crystals. The material has little appeal except for its extreme scarcity. Stones often have a slight milky or cloudy look, and anything over 3 carats is likely to be included.
Name: From the Greek leukos, meaning white.
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