metamorphic
Quartzite
Quartzite (SiO2)
Hardness: 7 on Mohs scale; Color: Grayish-white with some opacity; Luster: Vitreous to dull; Crystal structure: Trigonal/Hexagonal (granular); Cleavage: None (conchoidal fracture).
- Hardness
- 7 on Mohs scale
- Color
- Grayish-white with some opacity
- Luster
- Vitreous to dull
Identified More metamorphic →
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Physical properties
Hardness: 7 on Mohs scale; Color: Grayish-white with some opacity; Luster: Vitreous to dull; Crystal structure: Trigonal/Hexagonal (granular); Cleavage: None (conchoidal fracture).
Formation & geological history
Forms through the regional metamorphism of quartz sandstone. High heat and pressure cause quartz grains to recrystallize and fuse together, creating a very hard, dense rock.
Uses & applications
Used in construction for road ballast, flooring, and wall coverings. Also used as a high-purity silica source in glassmaking and as decorative garden stones.
Geological facts
Quartzite is so strong that when it breaks, it fractures through the quartz grains rather than along the boundaries between them, unlike its parent stone, sandstone.
Field identification & locations
Identify in the field by its extreme hardness (it will easily scratch glass) and its sugary, crystalline surface texture. It often forms prominent ridges because it is highly resistant to weathering.
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