Quartzite

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

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.

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.

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.

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.