Quartzite

Physical Properties

Hardness: 7 on Mohs scale; Color: typically white, gray, or tan, but often pink or reddish due to iron oxides; Luster: vitreous to dull; Crystal structure: hexagonal (microcrystalline); Cleavage: none; Specific gravity: approx. 2.65.

Formation & Geological History

Formed through the metamorphism of quartz sandstone under intense heat and pressure, usually associated with regional tectonic activity. The individual quartz grains recrystallize and fuse into an interlocking mosaic.

Uses & Applications

Used as crushed stone in construction and road building, as a high-silica raw material in manufacturing, and as decorative stone for countertops, tiles, and landscaping.

Geological Facts

Quartzite is so tough that it often breaks through the constituent sand grains rather than around them, which distinguishes it from sandstone. Some rare varieties, like 'Sodalite Quartzite,' are used as semi-precious gemstones.

Field Identification & Locations

Identify in the field by its extreme hardness (it will easily scratch glass and steel) and its grainy but fused appearance. Found in mountain ranges and ancient shields worldwide, such as the Appalachians or the Scottish Highlands.

Identified on: 5/13/2026

Mode: Standard