metamorphic
Quartzite
Quartzite (SiO2)
Hardness: 7 on Mohs scale. Color: Grayish-white to light blue-gray. Luster: Vitreous to dull. Crystal structure: Hexagonal (microcrystalline). Texture: Granular, non-foliated. Specific gravity: 2.6-2.7.
- Hardness
- 7 on Mohs scale
- Color
- Grayish-white to light blue-gray
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale. Color: Grayish-white to light blue-gray. Luster: Vitreous to dull. Crystal structure: Hexagonal (microcrystalline). Texture: Granular, non-foliated. Specific gravity: 2.6-2.7.
Formation & geological history
Formed through the regional or contact metamorphism of quartz-rich sandstone. High heat and pressure cause the original quartz grains to recrystallize, interlocking them into a very hard, dense rock.
Uses & applications
Used in construction for road ballast, floor tiles, and countertop surfaces. Also used as a decorative stone and occasionally as a source of silica in glass manufacturing.
Geological facts
Quartzite is so hard that it will scratch glass and steel. It often forms resistant ridges in mountain ranges because it is much more weather-resistant than the rocks surrounding it.
Field identification & locations
Identify in the field by its sugary texture and extreme hardness (it will not be scratched by a knife). It lacks the internal layers of schist or gneiss. Found in metamorphic belts worldwide.
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