Quartzite

Physical Properties

Hardness: 7 (Mohs), Color: Off-white to tan/yellowish, Luster: Vitreous to dull, Structure: Granular/Crystalline, Cleavage: None (conchoidal fracture), Specific Gravity: 2.6-2.7

Formation & Geological History

Formed from the metamorphism of quartz sandstone under high heat and pressure, where individual quartz grains recrystallize into a dense interlocking mosaic. Found in orogenic belts worldwide.

Uses & Applications

Used in construction for road ballast, flooring, and wall coverings; high-purity varieties are used to produce glass and industrial silica.

Geological Facts

Quartzite is so tough that it usually breaks through the quartz grains rather than along the boundaries between them, unlike sandstone. It is often harder than steel.

Field Identification & Locations

Identify in the field by its hardness (scratches glass) and sugary, crystalline appearance on fresh surfaces. Commonly found in mountainous regions or as rounded river cobbles due to its durability.

Identified on: 5/3/2026

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