metamorphic
Quartzite
Quartzite (SiO2)
Hardness: 7 on Mohs scale; Color: Light gray, white, or pale green; Luster: Vitreous to dull; Crystal structure: Hexagonal (trigonal); Cleavage: None; Specific gravity: 2.6-2.7
- Hardness
- 7 on Mohs scale
- Color
- Light gray, white, or pale green
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: Light gray, white, or pale green; Luster: Vitreous to dull; Crystal structure: Hexagonal (trigonal); Cleavage: None; Specific gravity: 2.6-2.7
Formation & geological history
Formed from the metamorphism of quartz-rich sandstone under intense heat and pressure, typically during mountain-building events (orogenic cycles).
Uses & applications
Used in construction as crushed stone for road gravel, as decorative stone in architecture, and as a source of silica in glass manufacturing.
Geological facts
Quartzite is so tough that it often outlasts the surrounding rock during erosion, frequently forming the tops of ridges and mountains.
Field identification & locations
Identify in the field by its extreme hardness (it will scratch glass and steel) and its grainy, sandpaper-like texture that unlike sandstone, breaks across the grains rather than around them.
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