metamorphic
Quartzite
Quartzite (primarily SiO2)
Hardness: 7 on Mohs scale; Color: White, grey, or tan; Luster: Vitreous to dull; Crystal structure: Non-foliated, granular; Specific gravity: 2.6-2.7
- Hardness
- 7 on Mohs scale
- Color
- White, grey, or tan
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: White, grey, or tan; Luster: Vitreous to dull; Crystal structure: Non-foliated, granular; Specific gravity: 2.6-2.7
Formation & geological history
Formed when quartz-rich sandstone is subjected to high heat and pressure, causing the individual quartz grains to recrystallize and fuse together. It can be found in mountain ranges and plateaus of any geological age.
Uses & applications
Used as crushed stone for road construction, railway ballast, and as a decorative stone in architecture and landscaping. High-purity quartzite is used to produce silica sand for glass making.
Geological facts
Quartzite is so strong and resistant to chemical weathering that it often forms the ridges and peaks of mountain ranges because it wears away much slower than the surrounding rocks.
Field identification & locations
Identify in the field by its hardness (it will scratch glass) and its sugary, granular texture. Unlike sandstone, it breaks through the grains rather than around them. Found globally in ancient shield areas and folded mountain belts.
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