Quartzite

Physical Properties

Hardness: 7 on Mohs scale; Color: typically white, gray, or pink; Luster: vitreous to dull; Crystal structure: hexagonal (but grains are interlocking); Cleavage: none; Specific Gravity: 2.6–2.7

Formation & Geological History

Formed through the regional or contact metamorphism of quartz-rich sandstone. Under high heat and pressure, the individual quartz grains recrystallize into a dense, interlocking mosaic of crystals. It can date from almost any geological era containing sandstone beds.

Uses & Applications

Used as crushed stone for road construction and railway ballast; also used as a decorative stone in architecture, countertops, and flooring due to its extreme durability and resistance to weathering.

Geological Facts

Quartzite is so hard and chemically resistant that it often forms the tops of ridges and mountains because it resists erosion better than the surrounding rock types. It will scratch glass easily.

Field Identification & Locations

Identify in the field by its sugary texture and the fact that it breaks across grain boundaries rather than around them (unlike sandstone). Found globally in mountainous regions and areas of ancient crustal uplift like the Appalachians or the Alps.

Identified on: 4/27/2026

Mode: Standard