Quartzite

Physical Properties

Hardness: 7 on Mohs scale; Color: typically white, gray, or tan (due to iron oxides); Luster: vitreous to grainy; Crystal structure: Trigonal (microcrystalline); Cleavage: none, breaks with a conchoidal or irregular fracture; Specific gravity: 2.6 to 2.7.

Formation & Geological History

Formed through the regional or contact metamorphism of quartz-rich sandstone. Under high heat and pressure, quartz grains recrystallize and fuse together. It can be found in mountain belts and Precambrian terrains worldwide.

Uses & Applications

Used extensively in construction as crushed stone for road bases and railway ballast. Due to its resistance to weathering and heat, it is used for countertops, wall veneers, and as a decorative stone in landscaping.

Geological Facts

Quartzite is so hard and chemically resistant that it often forms the caps of hills and mountains through differential weathering. It can be distinguished from its parent rock, sandstone, by the fact that it breaks through quartz grains rather than around them.

Field Identification & Locations

Identify in the field by its extreme hardness (cannot be scratched by steel) and lack of reaction to acid. It often feels sandpaper-like but the individual grains are fused. Common in riverbeds and mountainous glacial deposits.

Identified on: 5/16/2026

Mode: Standard