metamorphic
Quartzite
Quartzite (SiO2 composition)
AI-generated identification · may be incorrectHardness: 7 on the Mohs scale; Color: light gray to off-white with sugary texture; Luster: vitreous to dull; Crystal Structure: granoblastic (interlocking quartz grains); Cleavage: none (fractures conchoidally or irregularly); Specific Gravity: ~2.65
- Hardness
- 7 on the Mohs scale
- Color
- light gray to off-white with sugary texture
- Luster
- vitreous to dull
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Physical properties
Hardness: 7 on the Mohs scale; Color: light gray to off-white with sugary texture; Luster: vitreous to dull; Crystal Structure: granoblastic (interlocking quartz grains); Cleavage: none (fractures conchoidally or irregularly); Specific Gravity: ~2.65
Formation & geological history
Formed through regional or thermal metamorphism of quartz-rich sandstone under high heat and intense pressure, causing individual quartz grains to recrystallize into a interlocking mosaic.
Uses & applications
Widely used as crushed stone in road construction, railway ballast, building stone, decorative landscaping stone, and as a source of high-purity silica for glass and metal manufacturing.
Geological facts
Unlike sandstone, which breaks along grain boundaries, quartzite breaks directly across its quartz grains due to its densely fused crystalline structure.
Field identification & locations
Identified by its extreme hardness (scratches glass easily), granular crystalline appearance, and resistance to chemical weathering. Commonly found in mountainous regions, ancient metamorphic shields, and eroded ridge caps globally.
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