metamorphic
Quartzite
Metamorphic Quartzite (predominantly SiO2)
AI-generated identification · may be incorrectHardness: 7 on Mohs scale; Color: whitish-gray to pale cream with a sugary texture; Luster: vitreous to dull/greasy; Crystal structure: Trigonal (microscopic interlocking quartz grains); Cleavage: none (conchoidal to uneven fracture); Specific gravity: ~2.65.
- Hardness
- 7 on Mohs scale
- Color
- whitish-gray to pale cream with a sugary texture
- Luster
- vitreous to dull/greasy
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Physical properties
Hardness: 7 on Mohs scale; Color: whitish-gray to pale cream with a sugary texture; Luster: vitreous to dull/greasy; Crystal structure: Trigonal (microscopic interlocking quartz grains); Cleavage: none (conchoidal to uneven fracture); Specific gravity: ~2.65.
Formation & geological history
Formed through the regional or contact metamorphism of quartz-rich sandstone under intense heat and tectonic pressure. The original sand grains recrystallize into a dense, interlocking mosaic of quartz crystals.
Uses & applications
Extensively used as crushed stone for railway ballast, road base, and construction aggregate. Also cut and polished for decorative building facades, countertops, and dimension stone.
Geological facts
Unlike sandstone which fractures around individual sand grains, quartzite is so strongly recrystallized that it fractures directly through the quartz grains, leaving a smooth or glassy fracture surface.
Field identification & locations
Identifiable by its high hardness (easily scratches glass and steel), granular sugary appearance, and lack of reaction to dilute hydrochloric acid. Abundant globally in riverbeds, glacial tills, and folded mountain belts.
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