metamorphic
Quartzite
Quartzite (SiO2)
Hardness: 7 on Mohs scale; Color: typically white to gray, but pink, red, or tan due to iron oxides; Luster: Vitreous to dull; Crystal structure: Trigonal (microcrystalline); Cleavage: None, fractures conchoidally.
- Hardness
- 7 on Mohs scale
- Luster
- Vitreous to dull
Identified More metamorphic →
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Physical properties
Hardness: 7 on Mohs scale; Color: typically white to gray, but pink, red, or tan due to iron oxides; Luster: Vitreous to dull; Crystal structure: Trigonal (microcrystalline); Cleavage: None, fractures conchoidally.
Formation & geological history
Formed through the metamorphism of quartz-rich sandstone under intense heat and pressure, typically during mountain-building events (orogeny). The original sand grains recrystallize into a locked mosaic of quartz crystals.
Uses & applications
Used in construction as crushed stone for road ballast, as a decorative dimension stone in countertops and wall coverings, and historically as a material for stone tools.
Geological facts
Quartzite is so tough that it often outlasts the surrounding rocks, forming high ridges and resistant mountains. It is harder than steel and will easily scratch glass.
Field identification & locations
Identified in the field by its extreme hardness and its sugary, crystalline texture that breaks across grain boundaries rather than around them. Commonly found in folded mountain belts globally.
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