metamorphic
Quartzite
Quartzite (composed primarily of SiO2)
Hardness: 7 on Mohs scale; Color: Grayish-white; Luster: Vitreous to dull; Structure: Non-foliated, granular texture; Cleavage: None (conchoidal fracture).
- Hardness
- 7 on Mohs scale
- Color
- Grayish-white
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: Grayish-white; Luster: Vitreous to dull; Structure: Non-foliated, granular texture; Cleavage: None (conchoidal fracture).
Formation & geological history
Forms through the regional metamorphism of quartz-rich sandstone under high heat and pressure, causing quartz grains to recrystallize and fuse together.
Uses & applications
Commonly used as crushed stone in road construction, as railway ballast, and in the manufacturing of glass and ceramics. Pure forms are used for countertops and building stone.
Geological facts
Quartzite is so tough that it often outlasts other surrounding rocks during erosion, frequently forming the caps of hills and mountains. It is harder than steel.
Field identification & locations
Identified in the field by its extreme hardness (cannot be scratched by a knife) and its grainy, sugary appearance. It breaks across the grains rather than around them, unlike sandstone.
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