Quartzite (River Stone)

Physical Properties

Hardness: 7 (Mohs scale); Color: Off-white to tan/beige; Luster: Vitreous to dull; Crystal structure: Hexagonal/Trigonal system (macrocrystalline); Specific gravity: 2.6-2.7

Formation & Geological History

Formed through the metamorphism of quartz-rich sandstone. High heat and pressure reciprocal the original sand grains together into a dense, crystalline mass. This specific specimen shows rounding from water erosion (fluvial transport).

Uses & Applications

Used in construction as road ballast, gravel, and dimension stone. Occasionally used in jewelry as 'river pebbles' or in decorative landscaping.

Geological Facts

Quartzite is so tough that it often outlasts the surrounding rock in high-erosion environments; some of the oldest desert dunes and mountaintops are composed of resistant quartzite remnants.

Field Identification & Locations

Identify by its ability to scratch glass and its grainy, sandpaper-like texture that lacks visible individual sand grains (unlike original sandstone). Frequently found in riverbeds and glacial deposits.

Identified on: 4/13/2026

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