metamorphic
Quartzite
Quartzite (primarily SiO2)
Hardness: 7 on Mohs scale; Color: Grayish-white to tan; Luster: Vitreous to dull; Crystal structure: Non-foliated, granular; Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.7
- Hardness
- 7 on Mohs scale
- Color
- Grayish-white to tan
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: Grayish-white to tan; Luster: Vitreous to dull; Crystal structure: Non-foliated, granular; Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.7
Formation & geological history
Formed through the metamorphism of quartz-rich sandstone under intense heat and pressure, typically during mountain-building events (orogeny). Common in Precambrian formations.
Uses & applications
Used as crushed stone for road construction, railway ballast, and as a raw material in glass manufacturing. High-quality specimens are used for countertops and floor tiles.
Geological facts
Quartzite is so tough that it often survives intense weathering and erosion that destroys other rocks, often forming the peaks of rugged mountain ranges.
Field identification & locations
Identify by its ability to scratch glass and its granular, sugary appearance when broken. It is a common glacial erratic found in riverbeds and landscaping gravel.
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