Quartzite

Physical Properties

Hardness: 7 (Mohs scale); Color: Gray, white, or yellowish; Luster: Vitreous to dull; Crystal structure: Hexagonal (microcrystalline); Cleavage: None, exhibits conchoidal fracture; Specific gravity: 2.6-2.7.

Formation & Geological History

Formed through the metamorphism of quartz-rich sandstone. High heat and pressure cause the quartz grains to recrystallize and fuse together. Typically found in mountain-building regions (orogenic belts).

Uses & Applications

Used as a decorative stone in architecture, as crushed stone for road construction and railway ballast, and occasionally for high-silica industrial processes.

Geological Facts

Quartzite is so hard and chemically resistant that it often forms the ridges and caps of mountain ranges, weathering much slower than the rocks surrounding it.

Field Identification & Locations

Identify in the field by its extreme hardness (it will scratch glass easily) and its sugary texture where broken. Unlike sandstone, it breaks through the quartz grains rather than around them.

Identified on: 4/27/2026

Mode: Standard