metamorphic
Quartzite
Quartzite (SiO2)
Hardness: 7 on Mohs scale; Color: Light gray, whitish, with yellowish/brown iron oxide staining; Luster: Vitreous to dull; Crystal structure: Hexagonal (microcrystalline aggregate); Cleavage: None (conchoidal to uneven fracture); Specific Gravity: ~2.65
- Hardness
- 7 on Mohs scale
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: Light gray, whitish, with yellowish/brown iron oxide staining; Luster: Vitreous to dull; Crystal structure: Hexagonal (microcrystalline aggregate); 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 pressure, causing quartz grains to recrystallize and interlock tightly.
Uses & applications
Used as crushed stone for construction, road ballast, decorative landscaping stone, and occasionally as dimension stone or flux in metallurgy.
Geological facts
Quartzite is so tough that when it breaks, it fractures through the quartz grains rather than along the boundaries between them, unlike its parent rock sandstone.
Field identification & locations
Identified in the field by its high hardness (scratches glass easily) and granular sugary texture. Commonly found in mountainous regions, ancient shield areas, and riverbeds.
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