Quartzite

Physical Properties

Hardness: 7 on Mohs scale; Color: Light gray to white; Luster: Vitreous to dull; Crystal structure: Trigonal/Hexagonal; Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.7

Formation & Geological History

Formed through the regional metamorphism of quartz-rich sandstone. High heat and pressure cause the quartz grains to recrystallize and fuse together, forming a dense, interlocking matrix.

Uses & Applications

Used in construction as crushed stone for road beds, railway ballast, and decorative building stone. In ground form, it is used high-purity glass manufacturing and ceramics.

Geological Facts

Quartzite is so tough that it often outlasts the surrounding rock in the landscape, frequently forming the tops of ridges and hills. It is harder and more durable than the parent sandstone.

Field Identification & Locations

Identify in the field by its grainy texture that looks like sandstone but does not break around the grains; instead, it breaks through them. Found globally in ancient mountain belts and shield areas.

Identified on: 4/22/2026

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