metamorphic
Quartzite
Quartzite (SiO2)
Hardness: 7 on Mohs scale; Color: White to light grey with greenish tints; Luster: Vitreous to dull; Crystal structure: Trigonal/Hexagonal (granular texture); Specific gravity: 2.6-2.7
- Hardness
- 7 on Mohs scale
- Color
- White to light grey with greenish tints
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: White to light grey with greenish tints; Luster: Vitreous to dull; Crystal structure: Trigonal/Hexagonal (granular texture); Specific gravity: 2.6-2.7
Formation & geological history
Formed through the metamorphism of quartz-rich sandstone. Heat and pressure recrystallize the sand grains into a dense, interlocking matrix of quartz crystals.
Uses & applications
Used in construction as road ballast, gravel, and building stone. Highly pure varieties can be used as a source of silica for glassmaking and industrial abrasives.
Geological facts
Quartzite is so tough that it usually breaks through the quartz grains rather than along their boundaries. It is more resistant to weathering than the sandstone from which it originated.
Field identification & locations
Identify by its hardness (it will easily scratch glass) and its sugary, granular texture. Often found in mountain ranges and areas with ancient continental shields.
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