Quartzite

Physical Properties

Hardness: 7 on Mohs scale (scratches glass); Color: White, gray, or yellowish due to impurities; Luster: Vitreous to dull; Crystal structure: Trigonal (microcrystalline); Cleavage: None (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 sand grains to recrystallize and fuse together. Specimens are found in mountain belts and areas of ancient tectonic activity.

Uses & Applications

Used widely in construction as decorative stone, crushed stone for road beds, railway ballast, and in the manufacturing of silica glass or ceramics.

Geological Facts

Quartzite is so tough that it often outlasts many other rocks in weathering, frequently forming the rugged ridges or caps of mountain ranges. It is harder than the sandstone it originated from.

Field Identification & Locations

Identify in the field by its extreme hardness (cannot be scratched by a steel knife) and its grainy appearance that looks like sandpaper but feels smooth and solid. Found globally in metamorphic terrains.

Identified on: 4/27/2026

Mode: Standard