metamorphic
Quartzite
Quartzite (composed primarily of Silicon Dioxide, SiO2)
Hardness: 7 on Mohs scale; Color: Grayish-white with some inclusions; Luster: Vitreous to dull; Crystal structure: Trigonal (granular); Cleavage: None; Specific gravity: 2.6-2.7
- Hardness
- 7 on Mohs scale
- Color
- Grayish-white with some inclusions
- Luster
- Vitreous to dull
Identified More metamorphic →
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Physical properties
Hardness: 7 on Mohs scale; Color: Grayish-white with some inclusions; Luster: Vitreous to dull; Crystal structure: Trigonal (granular); Cleavage: None; Specific gravity: 2.6-2.7
Formation & geological history
Formed from the metamorphism of quartz-rich sandstone. High heat and pressure cause the quartz grains to recrystallize and fuse together, losing the original grain structure and becoming a dense, hard rock.
Uses & applications
Used in construction as crushed stone for road beds, railway ballast, and decorative stone. Historically used for making tools due to its hardness. High-purity quartzite is also a source of silica for glass and chemical industries.
Geological facts
Quartzite is so hard that it will scratch glass and steel. Unlike sandstone, which breaks around grains, quartzite breaks through the grains when fractured due to its extreme recrystallization.
Field identification & locations
Identify by its extreme hardness and sugary or granular appearance on fresh surfaces. It is found in mountain ranges worldwide where tectonic forces have compressed sediment layers. Look for it in glaciated regions or river beds as durable cobbles.
