Quartzite Pebble (River Rock)

Physical Properties

Hardness: 7 on Mohs scale; Color: grayish-white to tan; Luster: vitreous to dull; Crystal structure: Hexagonal (microcrystalline); Cleavage: none (conchoidal fracture); Specific gravity: 2.6-2.7

Formation & Geological History

Formed through the metamorphism of quartz-rich sandstone under intense heat and pressure. This specific specimen has been further shaped and smoothed by fluvial (river) erosion over thousands of years.

Uses & Applications

Used primarily as decorative landscaping stone, in construction aggregates, and occasionally as a source of silica for glass making.

Geological Facts

Quartzite is so tough that it often outlasts the mountains it was formed in; it is more durable than its parent rock (sandstone) and even granite. This pebble's smooth surface indicates a long journey in a river or coastal environment.

Field Identification & Locations

Identify by its ability to scratch glass and lack of reaction to acid. Look for a dense, sugary or crystalline texture on fresh breaks. Commonly found in riverbeds and glacial deposits worldwide.

Identified on: 4/23/2026

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