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Nepheline (Na,K)AlSiO4
Class: Silicate
Subclass: Framework
Hardness: 5.5 - 6
Density: 2.5 - 2.7
Streak: White
Luster: Vitreous
Colors: White-gray-brownish
Crystal System: Hexagonal
Cleavage: Indistinct
Fracture: Conchoidal
Magnetism: None
Reaction with HCl: Very weak
Identification in hand sample:
Resembles quartz but instead is softer.
Industrial / economic uses:
Used in the manufacture of ceramics and glass.
Comments:
Looks like quartz/granite cross. Found in silica-poor alkaline igneous rocks.