metamorphic
Quartzite
Quartzite (primarily SiO2)
Hardness: 7 on Mohs scale; Color: typically white, gray, or reddish-brown (pictured); Luster: vitreous to dull; Crystal structure: granular, non-foliated; Cleavage: none (conchoidal fracture).
- Hardness
- 7 on Mohs scale
- Color
- typically white, gray, or reddish-brown (pictured)
- Luster
- vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: typically white, gray, or reddish-brown (pictured); Luster: vitreous to dull; Crystal structure: granular, non-foliated; Cleavage: none (conchoidal fracture).
Formation & geological history
Formed through the metamorphism of quartz sandstone under high heat and pressure, causing individual quartz grains to recrystallize into a locked mosaic structure.
Uses & applications
Used as crushed stone for road construction, railway ballast, manufacturing glass, decorative stone in architecture, and as abrasive material.
Geological facts
Quartzite is so tough that it often breaks through the quartz grains rather than along their boundaries. It is often more resistant to weathering than the surrounding rock, often forming ridges.
Field identification & locations
Identify in the field by its extreme hardness (cannot be scratched by steel) and its grainy, sandpaper-like texture that doesn't rub off. Common in mountainous regions with folded strata.
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