Quartzite

Physical Properties

Hardness: 7 (Mohs scale). Color: White, gray, brownish, with hints of yellow/orange from iron staining. Luster: Vitreous to waxy. Crystal structure: Trigonal/Hexagonal (microcrystalline). Cleavage: None (conchoidal fracture).

Formation & Geological History

Formed from the metamorphism of quartz sandstone under intense heat and pressure. This specific beach-worn specimen exhibits rounding from wave action and mechanical weathering.

Uses & Applications

Used in construction as crushed stone or decorative gravel. High-purity quartzite is used to produce silica sand for glassmaking and silicon industrial products.

Geological Facts

Quartzite is so hard and chemically resistant that it often forms the peaks of mountain ranges because it resists erosion better than the rocks surrounding it.

Field Identification & Locations

Identify by its ability to scratch glass easily and its lack of reaction to acid. Commonly found in metamorphic terrains or as rounded pebbles on beaches and in riverbeds.

Identified on: 5/3/2026

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