Quartzite

Physical Properties

Hardness: 7 on Mohs scale. Color: White to grey, with reddish or brownish tints from iron impurities. Luster: Vitreous to dull. Crystal structure: Trigonal (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, typically during mountain-building events (orogeny). This process causes the original quartz grains to recrystallize and fuse together.

Uses & Applications

Used widely in construction as crushed stone for road beds and railway ballast. Due to its hardness and resistance to weathering, it is used for floor tiles, countertops, and decorative landscaping stone.

Geological Facts

Quartzite is so hard and chemically resistant that it often forms the peaks of mountain ranges because it weathers much more slowly than the surrounding rock. It was used by prehistoric humans to make stone tools when flint was unavailable.

Field Identification & Locations

Identify in the field by its hardness (it will easily scratch glass and steel) and its crystalline, sugary appearance on fresh breaks. Unlike sandstone, quartzite breaks across the grain rather than around the sand grains. It is found in metamorphic belts worldwide.

Identified on: 4/15/2026

Mode: Standard