metamorphic

Quartzite

Metamorphosed Quartz Sandstone (SiO2)

AI-generated identification · may be incorrect

Hardness: 7 (Mohs scale), Color: White, gray, or tan with reddish tints from iron, Luster: Vitreous to dull, Crystal Structure: Trigonal, Cleavage: None (conchoidal fracture), Specific Gravity: 2.65

Identified February 9, 2026More metamorphic →

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Physical properties

Hardness: 7 (Mohs scale), Color: White, gray, or tan with reddish tints from iron, Luster: Vitreous to dull, Crystal Structure: Trigonal, Cleavage: None (conchoidal fracture), Specific Gravity: 2.65

Formation & geological history

Formed through the metamorphism of quartz sandstone under intense heat and pressure, causing the original quartz grains to recrystallize into an interlocking mosaic of crystals.

Uses & applications

Used extensively in road construction ballast, as a high-quality building stone, in the manufacture of glass and ceramics, and as a decorative stone in landscaping.

Geological facts

Quartzite is so tough that it often outlasts the mountain ranges in which it is formed, and it is frequently found as river-worn pebbles and cobbles due to its extreme resistance to weathering.

Field identification & locations

Identified by its sugary texture and extreme hardness (it will easily scratch glass). Commonly found in ancient mountain belts and glacial till; collectors should look for its semi-translucent appearance and lack of mineral grains compared to granite.