metamorphic
Quartzite
Quartzite (SiO2)
Hardness: 7 on Mohs scale; Color: typically white to gray, often with reddish-brown or pink tints from iron oxides; Luster: vitreous to dull; Crystal structure: hexagonal (microcrystalline); Cleavage: none, breaks with a conchoidal or irregular fracture.
- Hardness
- 7 on Mohs scale
- Luster
- vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: typically white to gray, often with reddish-brown or pink tints from iron oxides; Luster: vitreous to dull; Crystal structure: hexagonal (microcrystalline); Cleavage: none, breaks with a conchoidal or irregular fracture.
Formation & geological history
Formed from the regional or contact metamorphism of quartz-rich sandstone. High heat and pressure cause quartz grains to recrystallize and fuse into a dense, interlocking network of crystals.
Uses & applications
Used in construction as crushed stone for road beds, as a decorative stone in architecture (flooring, wall coverings), and as a raw material in the glass and silicate industries.
Geological facts
Quartzite is so tough that it often survives erosion better than almost any other rock, forming prominent ridges and peaks in mountainous terrain. It was historically used to make stone tools because it breaks into sharp edges.
Field identification & locations
Identify by its extreme hardness (cannot be scratched by a steel knife) and grainy, sugary texture. Unlike sandstone which breaks around grains, quartzite breaks through the grains. Common in folded mountain belts and ancient shield areas.
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