metamorphic
Quartzite
Quartzite (SiO2)
Hardness: 7 on Mohs scale; Color: typically white, gray, or tan but can be reddish due to iron oxides; Luster: vitreous to dull; Crystal structure: Trigonal (microcrystalline); Cleavage: none; Specific gravity: approx. 2.65.
- Hardness
- 7 on Mohs scale
- Luster
- vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: typically white, gray, or tan but can be reddish due to iron oxides; Luster: vitreous to dull; Crystal structure: Trigonal (microcrystalline); Cleavage: none; Specific gravity: approx. 2.65.
Formation & geological history
Formed from the regional or contact metamorphism of quartz-rich sandstone. Under high heat and pressure, quartz grains recrystallize and fuse together, creating an extremely hard and durable rock.
Uses & applications
Frequently used as decorative stone in landscaping, crushed stone in road construction, and ballast in railways. Higher quality pieces are used for countertops or floor tiles.
Geological facts
Quartzite is so hard that it can scratch steel and glass. It is often confused with marble, but can be distinguished by its superior hardness and lack of reaction to acid.
Field identification & locations
Identify in the field by its sugary or crystalline texture and its inability to be scratched by a knife blade. It is commonly found in mountainous areas where tectonic plates have collided.
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