Quartzite

Physical Properties

Hardness: 7 on Mohs scale; Color: Grayish-white; Luster: Vitreous to dull; Crystal structure: Trigonal (microcrystalline); Cleavage: None/Conchoidal fracture; Specific gravity: 2.6-2.65.

Formation & Geological History

Formed from the metamorphism of quartz sandstone under intense heat and pressure, typically during mountain-building events (orogeny).

Uses & Applications

Used in construction as a decorative stone, road ballast, and in the manufacturing of glass and ceramics due to its high silica content.

Geological Facts

Quartzite is so tough that it often outlasts the surrounding rocks in weathering processes, frequently forming the peaks of ridges and mountains.

Field Identification & Locations

Identify by its extreme hardness (cannot be scratched by steel) and lack of reaction to acid. Commonly found in folded mountain belts globally. Tips for collectors: look for its sugary texture.

Identified on: 5/18/2026

Mode: Standard