metamorphic
Quartzite
Quartzite (SiO2)
Hardness: 7 on Mohs scale; Color: Pinkish-tan or light brown; Luster: Vitreous to dull; Crystal structure: Non-foliated, granular; Cleavage: None, exhibits conchoidal fracture; Specific gravity: 2.6-2.7
- Hardness
- 7 on Mohs scale
- Color
- Pinkish-tan or light brown
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: Pinkish-tan or light brown; Luster: Vitreous to dull; Crystal structure: Non-foliated, granular; Cleavage: None, exhibits conchoidal fracture; Specific gravity: 2.6-2.7
Formation & geological history
Formed from the regional metamorphism of quartz-rich sandstone subjected to high temperature and pressure. This recrystallization causes the quartz grains to interlock, creating a very hard, dense rock. Geological ages range from Precambrian to Cenozoic.
Uses & applications
Used in construction as a decorative stone, crushed stone for road ballast, and in the manufacturing of glass and ceramics due to its high silica content. Often used for flooring and counter tops.
Geological facts
Quartzite is so hard that it will scratch glass. It is often confused with marble, but unlike marble which is made of calcite, quartzite will not react (fizz) with hydrochloric acid. It is one of the most durable rocks on Earth's surface.
Field identification & locations
Identified in the field by its extreme hardness and tendency to break across quartz grains rather than around them. Common in folded mountain ranges. Collectors look for pieces with interesting color banding or embedded crystals.
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