metamorphic
Quartzite
Quartzite (Primary constituent: SiO2)
Hardness: 7 on Mohs scale; Color: typically white to gray, often with greenish tint due to impurities; Luster: Vitreous to dull; Crystal structure: Trigonal (granular texture); Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.7
- Hardness
- 7 on Mohs scale
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: typically white to gray, often with greenish tint due to impurities; Luster: Vitreous to dull; Crystal structure: Trigonal (granular texture); Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.7
Formation & geological history
Formed through the regional metamorphism of quartzose sandstone under intense heat and pressure. The individual quartz grains recrystallize and fuse together into a dense, crystalline mesh.
Uses & applications
Used as a decorative stone in architecture, as crushed stone for road construction and railway ballast, and in the manufacturing of glass and ceramics due to high silica content.
Geological facts
Quartzite is so tough that it often breaks through the actual sand grains rather than around them. It is one of the most durable rocks on the Earth's surface and often forms prominent ridges because it resists weathering.
Field identification & locations
Identify in the field by its extreme hardness (it will easily scratch glass and steel) and its crystalline, sugary appearance. It is commonly found in folded mountain belts globally. Tips for collectors: look for its characteristic sparkly appearance under sunlight.
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