Quartzite

Physical Properties

Hardness: 7 on Mohs scale; Color: white/light tan; Luster: vitreous to waxy; Crystal structure: Hexagonal (microcrystalline); Cleavage: none (conchoidal fracture); Specific gravity: 2.6 – 2.7

Formation & Geological History

Formed through the metamorphism of quartz-rich sandstone under extreme heat and pressure. This process causes the individual quartz grains to recrystallize and fuse into a dense, solid rock lattice.

Uses & Applications

Used in construction as road ballast, flooring, and wall facing. Sometimes used defensively as stone tools in history. High-purity quartzite is used to produce ferrosilicon and industrial silica sand.

Geological Facts

Quartzite is so tough that when it breaks, it fractures through the quartz grains rather than along the boundaries between them, unlike its parent sandstone.

Field Identification & Locations

Identify by its extreme hardness (it will easily scratch glass) and its sugary/crystalline texture on fresh surfaces. Often found in mountainous regions or ancient coastal deposits.

Identified on: 5/2/2026

Mode: Standard