metamorphic
Quartzite
Quartzite (SiO2)
Hardness: 7 on Mohs scale. Color: White to light gray. Luster: Vitreous to sugary/greasy. Crystal Structure: Trigonal/Hexagonal microscopic interlocking grains. Cleavage: None (conchoidal or irregular fracture). Specific Gravity: 2.6-2.7.
- Hardness
- 7 on Mohs scale
- Color
- White to light gray
- Luster
- Vitreous to sugary/greasy
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Physical properties
Hardness: 7 on Mohs scale. Color: White to light gray. Luster: Vitreous to sugary/greasy. Crystal Structure: Trigonal/Hexagonal microscopic interlocking grains. Cleavage: None (conchoidal or irregular fracture). Specific Gravity: 2.6-2.7.
Formation & geological history
Formed when quartz-rich sandstone is subjected to high heat, pressure, and chemical activity during regional metamorphism, fusing individual quartz grains together into a dense, crystalline rock.
Uses & applications
Used as crushed stone for road construction, railroad ballast, decorative landscaping stone, countertops, and historically as a raw material for stone tools.
Geological facts
Quartzite is extremely resistant to chemical weathering and erosion, often forming prominent ridges and hilltops. Unlike sandstone, when quartzite breaks, it fractures through the quartz grains rather than around them.
Field identification & locations
Identify in the field by its extreme hardness (scratches glass and steel easily), sugary crystalline texture, and inability to react with acid (unlike marble). Commonly found in mountain belts and Precambrian shield regions worldwide.
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