metamorphic
Quartzite
Quartzite (SiO2)
Hardness: 7 on Mohs scale; Color: Grayish-white to light brown; Luster: Vitreous to dull; Crystal structure: Trigonal/Hexagonal (granular texture); Cleavage: None; Specific gravity: 2.6-2.7
- Hardness
- 7 on Mohs scale
- Color
- Grayish-white to light brown
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: Grayish-white to light brown; Luster: Vitreous to dull; Crystal structure: Trigonal/Hexagonal (granular texture); Cleavage: None; Specific gravity: 2.6-2.7
Formation & geological history
Formed through the regional metamorphism of quartz-rich sandstone. It occurs when sandstone is subjected to intense heat and pressure, causing the quartz grains to recrystallize and fuse together.
Uses & applications
Used in construction for road ballast, floor tiles, and countertop surfaces; historically used for making stone tools; also used in glass manufacturing and as a source of silica.
Geological facts
Quartzite is so tough that it often survives erosion better than the surrounding rocks, frequently forming the peaks of mountain ranges. It is chemically stable and resistant to weathering.
Field identification & locations
Identify by its extreme hardness (it will scratch glass and steel) and its crystalline, sugary texture that resembles granulated sugar when broken. Found globally in ancient mountain belts.
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