metamorphic
Quartzite
Quartzite (chiefly SiO2)
Hardness: 7 on Mohs scale. Color: Grayish-tan to reddish-brown (likely due to iron oxide staining). Luster: Vitreous to dull. Structure: Non-foliated, granular. Cleavage: Indistinct.
- Hardness
- 7 on Mohs scale
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale. Color: Grayish-tan to reddish-brown (likely due to iron oxide staining). Luster: Vitreous to dull. Structure: Non-foliated, granular. Cleavage: Indistinct.
Formation & geological history
Formed through the metamorphism of quartz-rich sandstone under intense heat and pressure, typically during mountain-building events (orogeny). Often Proterozoic to Paleozoic in age.
Uses & applications
Used as crushed stone for road construction, railway ballast, and as a decorative stone in architecture or landscaping.
Geological facts
Quartzite is so hard that when it breaks, it fractures through the individual sand grains rather than around them, unlike its parent sandstone.
Field identification & locations
Identify by its extreme hardness (cannot be scratched by a steel nail) and grainy, crystalline texture. Commonly found in folded mountain belts globally.
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