metamorphic
Quartzite
Quartzite (SiO2-rich metamorphic rock)
Hardness: 7 on Mohs scale; Color: typically white to gray, occasionally pink or reddish; Luster: vitreous to dull; Crystal structure: granular/sugary texture; Cleavage: none (breaks with conchoidal fracture); Specific gravity: 2.6-2.7.
- Hardness
- 7 on Mohs scale
- Color
- typically white to gray, occasionally pink or reddish
- Luster
- vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: typically white to gray, occasionally pink or reddish; Luster: vitreous to dull; Crystal structure: granular/sugary texture; Cleavage: none (breaks with conchoidal fracture); Specific gravity: 2.6-2.7.
Formation & geological history
Formed through the metamorphism of quartz sandstone. Intense heat and pressure cause the quartz grains to recrystallize and fuse together. Often associated with continental mountain-building events.
Uses & applications
Used as crushed stone for road construction, railway ballast, and as a decorative stone in architecture. Also used in the production of glass and silicon due to high silica content.
Geological facts
Quartzite is so hard that it can scratch steel. Unlike sandstone, which breaks around its quartz grains, quartzite is so well-fused that it breaks through the grains when fractured.
Field identification & locations
Identify in the field by its sugary texture and extreme hardness (it will easily scratch glass). It is commonly found in ancient mountain ranges like the Appalachians or the Alps. It often forms prominent, weather-resistant ridges.
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