Quartzite

Physical Properties

Hardness: 7 on Mohs scale; Color: white to light gray with tan/brown staining; Luster: vitreous to dull; Crystal Structure: non-foliated, granular; Cleavage: none (conchoidal fracture); Specific Gravity: 2.6-2.7

Formation & Geological History

Formed through the regional or contact metamorphism of quartzose sandstone. Under intense heat and pressure, the original quartz grains recrystallize and fuse into a solid, interlocking mosaic of quartz crystals.

Uses & Applications

Used as a decorative stone in landscaping, a raw material in the manufacturing of glass and ceramics, as railway ballast, and occasionally as a building stone or countertop material.

Geological Facts

Quartzite is so tough that it often survives intense weathering better than other rocks, frequently forming the tops of ridges and mountains. It is distinguishably harder than the glass on most phone screens.

Field Identification & Locations

Identify in the field by its extreme hardness (it will easily scratch glass) and its granular, sugary appearance on a fresh break. Unlike sandstone, it breaks across the grain rather than around them. Found globally in mountainous regions.

Identified on: 4/22/2026

Mode: Standard