Quartzite pebble

Physical Properties

Hardness: 7 (Mohs scale), Color: Reddish-brown to tan, Luster: Vitreous to dull, Crystal structure: Trigonal (microcrystalline), Cleavage: None (conchoidal fracture), Specific gravity: 2.6-2.65

Formation & Geological History

Formed through the metamorphism of quartz sandstone under intense heat and pressure, typically during mountain-building events. This specimen has been rounded by fluvial or beach erosion.

Uses & Applications

Used as a decorative landscape stone, construction aggregate, and in high-purity forms for glass manufacturing or as a refractory material.

Geological Facts

Quartzite is so tough that it often survives multiple cycles of erosion, outlasting the source mountains from which it came. It is harder than steel and will scratch glass easily.

Field Identification & Locations

Identify by its hardness (will scratch a knife blade) and interlocking crystalline texture. Commonly found in riverbeds, glacial tills, and ancient mountain belts like the Appalachians or the Alps.

Identified on: 4/19/2026

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