Quartzite (River Stone)

Hardness: 7 (Mohs scale), Color: Creamy white to pale tan, Luster: Vitreous to waxy (especially when wet or polished), Crystal structure: Trigonal/Hexagonal, Cleavage: None (conchoidal fracture), Specific Gravity: 2.65

Quartzite is formed when quartz-rich sandstone is subjected to high heat and pressure, causing the original quartz grains to recrystallize and fuse together. This specific specimen has been further shaped and smoothed by water erosion in a river or beach environment.

Metamorphic quartzite is used in construction as crushed stone, for decorative landscaping, as a source for silica in glassmaking, and frequently as a collector's 'pocket stone' due to its smooth texture.

Quartzite is so strong and hard that it typically breaks through the quartz grains rather than along the boundaries between them, unlike sandstone. It is resistant to chemical weathering and often remains as a ridge or peak in mountainous terrain after softer rocks have eroded away.

Identify in the field by its inability to be scratched by a steel knife (unlike calcite) and its lack of reaction to acid. It is commonly found in ancient mountain belts and as rounded pebbles in stream beds across North America and Europe.