metamorphic
Quartzite
Quartzite (SiO2)
Hardness: 7 (Mohs scale), Color: White, gray, or yellowish tint, Luster: Vitreous to dull, Crystal Structure: Trigonal (granular texture), Cleavage: Indistinct, Specific Gravity: 2.6-2.7
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Physical properties
Hardness: 7 (Mohs scale), Color: White, gray, or yellowish tint, Luster: Vitreous to dull, Crystal Structure: Trigonal (granular texture), Cleavage: Indistinct, Specific Gravity: 2.6-2.7
Formation & geological history
Formed through the regional metamorphism of quartz-rich sandstone. High heat and pressure cause the sand grains to recrystallize and fuse together, losing the original sedimentary texture.
Uses & applications
Used in construction as crushed stone for road beds, as railway ballast, and in the production of glass and industrial silica. High-quality pieces are used for countertops and ornamental flooring.
Geological facts
Quartzite is so tough that it often fractures across the original sand grains rather than around them. It is one of the most chemically and physically resistant rocks found on Earth.
Field identification & locations
Identify by its extreme hardness (cannot be scratched by a steel nail) and grainy, sugary texture. It is commonly found in mountain ranges and areas with exposed metamorphic basement rock.
