Quartzite

Physical Properties

Hardness: 7 on Mohs scale; Color: Reddish-brown, purple, or gray due to iron oxides; Luster: Vitreous to dull; Crystal structure: Non-foliated, granular; Cleavage: None; Specific Gravity: 2.6-2.7.

Formation & Geological History

Formed through the regional metamorphism of quartzose sandstone. Under high heat and pressure, quartz grains recrystallize and fuse together. The sample appears to be from a Precambrian or Paleozoic formation.

Uses & Applications

Used as crushed stone for road construction, railway ballast, and as a decorative stone in landscaping. Historically used for making stone tools due to its conchoidal fracture and hardness.

Geological Facts

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

Field Identification & Locations

Identify in the field by its sugary texture and the way it breaks through the quartz grains rather than around them (unlike sandstone). Found globally in mountainous regions and ancient shield areas.

Identified on: 5/3/2026

Mode: Standard