Quartzite

Physical Properties

Hardness: 7 on Mohs scale; Color: typically white, gray, or reddish-brown (pictured); Luster: vitreous to dull; Crystal structure: granular, non-foliated; Cleavage: none (conchoidal fracture).

Formation & Geological History

Formed through the metamorphism of quartz sandstone under high heat and pressure, causing individual quartz grains to recrystallize into a locked mosaic structure.

Uses & Applications

Used as crushed stone for road construction, railway ballast, manufacturing glass, decorative stone in architecture, and as abrasive material.

Geological Facts

Quartzite is so tough that it often breaks through the quartz grains rather than along their boundaries. It is often more resistant to weathering than the surrounding rock, often forming ridges.

Field Identification & Locations

Identify in the field by its extreme hardness (cannot be scratched by steel) and its grainy, sandpaper-like texture that doesn't rub off. Common in mountainous regions with folded strata.

Identified on: 5/3/2026

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