Quartzite

Physical Properties

Hardness: 7 on Mohs scale; Color: typically white to gray, often yellow, brown, or pink due to iron impurities; Luster: Vitreous to dull; Crystal structure: Non-foliated, interlocking quartz crystals; Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.7

Formation & Geological History

Formed from the metamorphism of quartz-rich sandstone under intense heat and pressure. This specimen shows significant rounding from fluvial (river) or beach transport processes.

Uses & Applications

Used in construction as road ballast, gravel, and dimension stone. High-purity quartzite is used to produce silica sand for glassmaking and silicon for electronics.

Geological Facts

Quartzite is so hard and chemically resistant that it often forms the caps of ridges and mountains. It is harder than sandstone and will scratch glass easily.

Field Identification & Locations

Identify in the field by its hardness (cannot be scratched by a steel knife) and its grainy, sugary texture that resembles sandstone but does not rub off. Common in mountainous regions or as river pebbles.

Identified on: 4/15/2026

Mode: Standard