metamorphic
Quartzite
Quartzite (SiO2)
Hardness: 7 on Mohs scale; Color: light beige, off-white, light pinkish brown; Luster: sugary, vitreous to dull; Crystal structure: granoblastic; Cleavage: none (conchoidal to uneven fracture)
- Hardness
- 7 on Mohs scale
- Color
- light beige, off-white, light pinkish brown
- Luster
- sugary, vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: light beige, off-white, light pinkish brown; Luster: sugary, vitreous to dull; Crystal structure: granoblastic; Cleavage: none (conchoidal to uneven fracture)
Formation & geological history
Formed through the regional or contact metamorphism of quartz-rich sandstone under extreme heat and pressure, causing the original quartz grains to recrystallize into a interlocking mosaic of quartz crystals.
Uses & applications
Used as a decorative stone, dimension stone in construction, railway ballast, crushed stone for road base, and a raw source of silica in glassmaking and metallurgy.
Geological facts
Quartzite is so tough and resistant to chemical weathering that it often forms the tops of hills and mountain ridges, as surrounding softer rocks weather away.
Field identification & locations
Identified by its sugary granular texture and high hardness (scratches glass and steel easily). Unlike sandstone, quartzite fractures through the quartz grains rather than along grain boundaries.
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