Quartzite

Physical Properties

Hardness: 7 on Mohs scale; Color: white, gray, or greenish-gray; Luster: Vitreous to dull; Crystal structure: Trigonal/Hexagonal; Cleavage: None/Conchoidal fracture; Specific gravity: 2.6-2.7.

Formation & Geological History

Formed from the regional or contact metamorphism of quartz-rich sandstone. High heat and pressure cause quartz grains to recrystallize and fuse together, typically in orogenic belts.

Uses & Applications

Used extensively in the construction industry as crushed stone for road ballast, building material, and decorative landscaping stone. High-purity quartzite is used to produce glass and silicon metal.

Geological Facts

Quartzite is so tough that it often outlasts the rocks surrounding it, forming prominent ridges and peaks in mountain ranges. It is harder than steel and will scratch glass easily.

Field Identification & Locations

Identify in the field by its extreme hardness and tendency to break through quartz grains rather than around them (unlike sandstone). Found in mountain ranges and ancient shield areas worldwide.

Identified on: 5/1/2026

Mode: Standard