Quartzite

Physical Properties

Hardness: 7 on Mohs scale; Color: typically white, gray, or tan, but often yellow or orange due to iron staining as seen here; Luster: Vitreous to dull; Crystal structure: Non-foliated, granular; Specific gravity: approx 2.6-2.7.

Formation & Geological History

Formed from the metamorphism of quartz-rich sandstone subjected to high heat and pressure. The original sand grains recrystallize into a dense interlocking mosaic of quartz crystals.

Uses & Applications

Used as a high-quality railway ballast, crushed stone for road construction, architectural stone for countertops and floors, and as a raw material for glass and ceramics when pure.

Geological Facts

Quartzite is so tough that it often survives intense weathering better than other rocks, frequently capping hills and mountain ridges. It can be distinguished from its parent rock, sandstone, because it will break across the grains rather than around them.

Field Identification & Locations

Identify in the field by its extreme hardness (it will easily scratch glass and steel) and its granular, sugary appearance. Found globally in ancient mountain belts and areas of uplifted metamorphic basement rock.

Identified on: 4/14/2026

Mode: Standard