Chemistry: Complex sodium aluminum silicate
Crystal system: Cubic; dodecahedral or octahedral (rounded grains).
Color: Transparent to translucent; blue, white, gray, green, yellow, red.
Hardness: 6
Cleavage: Distinct: 1 direction; Fracture: brittle, conchoidal to uneven.
Specific gravity: 2.4
Refractive index: 1.496; SR (isotropic)
Luster: Vitreous to greasy.
Dispersion: -
Dichroism: -
Occurrence: Igneous rocks; under saturated lavas; Italy, Germany (Rhineland).
Notes
A constituent of lapis lazuli; sulphur-rich hauyne called ‘lazurite’; translucent and the rare type blue crystals cut for collectors; faceted, cabochon.
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