metamorphic
Quartzite
Quartzite (mainly SiO2)
Hardness: 7 (Mohs scale); Color: Pinkish-red, white, or tan; Luster: Vitreous to dull; Crystal structure: Trigonal/Hexagonal crystals within a sugary granular texture; Specific gravity: 2.6-2.7
- Hardness
- 7 (Mohs scale)
- Color
- Pinkish-red, white, or tan
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 (Mohs scale); Color: Pinkish-red, white, or tan; Luster: Vitreous to dull; Crystal structure: Trigonal/Hexagonal crystals within a sugary granular texture; Specific gravity: 2.6-2.7
Formation & geological history
Formed through the regional or contact metamorphism of quartzose sandstone. Intense heat and pressure cause the quartz grains to recrystallize and fuse together, often during mountain-building events.
Uses & applications
Used in construction as road ballast, railway track ballast, flooring, and decorative wall coverings. Fine specimens are used in landscaping and carvings.
Geological facts
Quartzite is so tough that it often breaks through the individual quartz grains rather than around them. In the Stone Age, it was sometimes used to make tools when flint was unavailable.
Field identification & locations
Identify by its extreme hardness (scratches glass) and granular texture. Often found in mountainous regions or as river-worn cobbles. It is more resistant to weathering than most other rocks.
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