metamorphic
Quartzite
Quartzite (SiO2)
Hardness: 7 (Mohs scale), Color: White to light grey, Luster: Vitreous/glassy to dull, Crystal structure: Trigonal (granular texture), Cleavage: None (conchoidal fracture), Specific Gravity: 2.6-2.7
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Physical properties
Hardness: 7 (Mohs scale), Color: White to light grey, Luster: Vitreous/glassy to dull, Crystal structure: Trigonal (granular texture), Cleavage: None (conchoidal fracture), Specific Gravity: 2.6-2.7
Formation & geological history
Formed through the regional metamorphism of quartz-rich sandstone subjected to high heat and pressure, causing the original quartz grains to recrystallize and fuse into a dense rock.
Uses & applications
Used in construction as road ballast, roofing material, and flooring. In crushed form, it is used for glass manufacturing and as industrial silica. Highly prized as a building stone for countertops and decorative walls.
Geological facts
Quartzite is so hard that it can scratch steel and is more resistant to weathering than the original sandstone. It often forms the prominent peaks of mountain ridges because it erodes so slowly.
Field identification & locations
Identify in the field by its interlocking crystalline texture and extreme hardness (it will easily scratch glass). Common in folded mountain belts and ancient continental shields worldwide.
