metamorphic
Quartzite
Quartzite (SiO2)
Hardness: 7 on Mohs scale. Color: tan, brownish-pink, or off-white. Luster: vitreous to sugary. Crystal Structure: trigonal (interlocking quartz grains). Cleavage: none, fractures conchoidally or irregularly through grains.
- Hardness
- 7 on Mohs scale
- Color
- tan, brownish-pink, or off-white
- Luster
- vitreous to sugary
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Physical properties
Hardness: 7 on Mohs scale. Color: tan, brownish-pink, or off-white. Luster: vitreous to sugary. Crystal Structure: trigonal (interlocking quartz grains). Cleavage: none, fractures conchoidally or irregularly through grains.
Formation & geological history
Formed from the regional or contact metamorphism of quartz-rich sandstone under intense heat and pressure, causing quartz grains to recrystallize into a dense interlocking network.
Uses & applications
Used as crushed stone in road construction, railway ballast, building stone, decorative landscaping stone, and as a source of silica in glassmaking.
Geological facts
Quartzite is so tough that when it breaks, the fractures cut directly through the quartz grains rather than around them, distinguishing it from sandstone.
Field identification & locations
Identify by its ability to scratch glass easily (Mohs 7) and its sugary, tightly interlocking granular texture. Commonly found in mountainous regions, riverbeds, and glacial deposits worldwide.
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