metamorphic
Quartzite
Quartzite (SiO2)
AI-generated identification · may be incorrectHardness: 7 on Mohs scale; Color: white, gray, or clouded; Luster: vitreous to dull; Crystal structure: Hexagonal (microcrystalline); Cleavage: none, shows conchoidal fracture; Specific gravity: 2.6-2.7.
- Hardness
- 7 on Mohs scale
- Color
- white, gray, or clouded
- Luster
- vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: white, gray, or clouded; Luster: vitreous to dull; Crystal structure: Hexagonal (microcrystalline); Cleavage: none, shows conchoidal fracture; Specific gravity: 2.6-2.7.
Formation & geological history
Formed through the regional or contact metamorphism of quartz-rich sandstone. Under intense heat and pressure, the individual quartz grains recrystallize and fuse together into a dense, hard rock.
Uses & applications
Used primarily in construction for crushed stone and road ballast. High-quality specimens are used for countertops, floor tiles, and as a decorative stone in landscaping. Also used in the production of glass and silicon.
Geological facts
Quartzite is so hard and chemically resistant that it often forms the tops of ridges and mountains because it resists erosion better than surrounding rocks. It can be distinguished from sandstone because it breaks across the grains rather than around them.
Field identification & locations
Identify in the field by its extreme hardness (it will easily scratch glass) and its sugary, crystalline texture. It is found worldwide in metamorphic mountain belts. Collectors look for pieces with interesting mineral inclusions or distinct coloration.
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