metamorphic
Quartzite
Quartzite (primarily SiO2)
Hardness: 7 on Mohs scale; Color: Pink, reddish, or white; Luster: Vitreous to dull; Crystal structure: Granoblastic (sugary texture); Cleavage: None (breaks across quartz grains); Specific gravity: 2.6-2.7
- Hardness
- 7 on Mohs scale
- Color
- Pink, reddish, or white
- Luster
- Vitreous to dull
Identified More metamorphic →
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Physical properties
Hardness: 7 on Mohs scale; Color: Pink, reddish, or white; Luster: Vitreous to dull; Crystal structure: Granoblastic (sugary texture); Cleavage: None (breaks across quartz grains); Specific gravity: 2.6-2.7
Formation & geological history
Formed through the regional or contact metamorphism of quartz-rich sandstone. Under high heat and pressure, the individual quartz grains recrystallize and fuse together. Many specimens date back to the Proterozoic or Paleozoic eras.
Uses & applications
Used widely in construction as crushed stone for road ballast, building stone, and floor tiles. It is also used as a source of silica for glass making and occasionally in jewelry as a decorative stone.
Geological facts
Quartzite is so tough that it often outlasts the surrounding rocks in mountainous areas, forming prominent ridges. It is often confused with sandstone, but can be distinguished because it breaks through the quartz grains rather than around them.
Field identification & locations
Identify in the field by its hardness (it will scratch glass) and its sugary, crystalline surface. It is commonly found in folded mountain belts and glaciated regions where it has been transported as cobbles.
