Quartzite

Physical Properties

Hardness: 7 on Mohs scale; Color: Tan, beige, white, grey; Luster: Vitreous to dull; Structure: Non-foliated, granoblastic; Fracture: Conchoidal; Specific Gravity: 2.6-2.7

Formation & Geological History

Formed through the metamorphism of quartz-rich sandstone. High heat and pressure cause the sand grains to recrystallize and fuse together, creating an extremely durable rock.

Uses & Applications

Used as crushed stone for road construction, railway ballast, and as a decorative stone in landscaping. High-purity quartzite is used to produce silica sand for glassmaking and silicon for electronics.

Geological Facts

Quartzite is so hard that it will scratch glass and steel. It is more resistant to weathering than the sandstone it originated from, often forming the resistant ridges of mountain ranges.

Field Identification & Locations

Identify in the field by its extreme hardness and the way it breaks through quartz grains rather than around them (unlike sandstone). It is commonly found in ancient mountain belts and riverbeds as rounded cobbles.

Identified on: 4/27/2026

Mode: Standard