metamorphic
Quartzite
Quartzite (SiO2)
Hardness: 7 on Mohs scale; Color: whitish-gray with iron oxide (rust) staining; Luster: Vitreous to dull; Crystal structure: Trigonal (granular texture); Cleavage: None (conchoidal fracture); Specific Gravity: 2.63-2.65
- Hardness
- 7 on Mohs scale
- Color
- whitish-gray with iron oxide (rust) staining
- Luster
- Vitreous to dull
Identified More metamorphic →
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Physical properties
Hardness: 7 on Mohs scale; Color: whitish-gray with iron oxide (rust) staining; Luster: Vitreous to dull; Crystal structure: Trigonal (granular texture); Cleavage: None (conchoidal fracture); Specific Gravity: 2.63-2.65
Formation & geological history
Formed through the metamorphism of quartz-rich sandstone. High heat and pressure cause the quartz grains to recrystallize and fuse together. Typically found in mountain ranges or ancient continental shields.
Uses & applications
Used primarily in construction as crushed stone for road ballast, roofing granules, and as a decorative stone. High-purity quartzite is used to produce glass and metallic silicon.
Geological facts
Quartzite is so tough that it often survives intense erosion to form the tops of ridges and mountains. It is harder than steel and will easily scratch glass.
Field identification & locations
Identify in the field by its extreme hardness and granular, sugary appearance. Unlike sandstone, which breaks around grains, quartzite breaks through the quartz grains themselves. Common worldwide in metamorphic terrains.
