Quartzite

Physical Properties

Hardness: 7 on Mohs scale; Color: typically white to gray, but can be pink or reddish; Luster: Vitreous to dull; Crystal structure: Trigonal (microcrystalline); Cleavage: None; Specific gravity: 2.6-2.7.

Formation & Geological History

Formed through the metamorphism of quartz sandstone under high heat and pressure. It originates from various geological eras, including the Precambrian remains of ancient beach or desert sands.

Uses & Applications

Used as crushed stone for road construction and railway ballast; decorative stone in architecture, countertops, and floor tiles; high-purity varieties are used to produce silica sand for glassmaking.

Geological Facts

Quartzite is so tough that it often outlasts the rock surrounding it, forming prominent ridges and peaks. It is often confused with marble, but can be distinguished by its superior hardness.

Field Identification & Locations

Identify by its ability to scratch glass and its granular, sugary texture. Common in mountain ranges and eroded riverbeds. Collectors look for unique colors or translucent qualities.

Identified on: 4/15/2026

Mode: Standard