metamorphic
Quartzite
Quartzite (SiO2)
Hardness: 7 on Mohs scale; Color: typically white, gray, or pink; Luster: vitreous (glassy) to dull; Crystal structure: trigonal/hexagonal; Cleavage: none (conchoidal fracture); Specific gravity: 2.63 - 2.65
- Hardness
- 7 on Mohs scale
- Color
- typically white, gray, or pink
- Luster
- vitreous (glassy) to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: typically white, gray, or pink; Luster: vitreous (glassy) to dull; Crystal structure: trigonal/hexagonal; Cleavage: none (conchoidal fracture); Specific gravity: 2.63 - 2.65
Formation & geological history
Formed through the regional or contact metamorphism of quartz-rich sandstone. High temperatures and pressures cause the quartz grains to recrystallize and fuse together, forming a dense, durable rock.
Uses & applications
Used in construction for road ballast, floor tiles, and countertop surfaces. Also used as a raw material for silica production and as a decorative stone in landscaping.
Geological facts
Quartzite is so hard and chemically resistant that it often forms prominent ridges and hills in mountainous regions because it resists weathering better than surrounding rocks.
Field identification & locations
Identify in the field by its extreme hardness (it will easily scratch glass) and its grainy, sugary appearance despite being a solid mass. It is found globally in Appalachian mountains (USA), Canada, and Brazil.
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