Quartzite

Physical Properties

Hardness: 7 on Mohs scale; Color: Tan, beige, or yellowish; 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 sandstone under high heat and pressure, typically during tectonic plate collisions. This specimen shows a granular, sugary texture typical of recrystallized quartz grains.

Uses & Applications

Used in construction as crushed stone, road ballast, or decorative building stone. In its purest forms, it is a source of silica for glassmaking and silicon production.

Geological Facts

Quartzite is so tough that it often outlasts other rocks during erosion, frequently forming the tops of mountain ranges and ridges.

Field Identification & Locations

Identify by its ability to scratch glass and its granular, sandpaper-like appearance that does not actually rub off. It typically breaks across the quartz grains rather than around them, unlike sandstone.

Identified on: 5/15/2026

Mode: Standard