Quartzite

Physical Properties

Hardness: 7 on Mohs scale. Color: Peach, tan, or reddish-pink due to iron oxide. Luster: Vitreous to waxy. Structure: Granular/crystalline with no cleavage. Specific Gravity: 2.6-2.7.

Formation & Geological History

Formed through the regional metamorphism of quartz-rich sandstone. Under high heat and pressure, original quartz grains recrystallize and fuse into a dense, interlocking matrix. It is found in mountain belts and shield areas.

Uses & Applications

Used primarily as decorative stone, crushed stone for road construction, railroad ballast, and occasionally for high-end countertops or as a source of silica in glassmaking.

Geological Facts

Quartzite is so tough that it often survives intense weathering better than the rocks surrounding it, forming the caps of ridges and mountains. It is harder than a steel knife and will scratch glass surfaces easily.

Field Identification & Locations

Identify in the field by its intense hardness (7) and 'sugary' texture. Unlike sandstone, when quartzite breaks, the fracture goes through the quartz grains rather than around them. Commonly found in riverbeds as rounded cobbles like this specimen.

Identified on: 5/2/2026

Mode: Standard