Quartzite

Physical Properties

Hardness: 7 on Mohs scale; Color: typically white to gray, but pink, orange, or yellow depending on impurities; Luster: vitreous to waxy; Crystal structure: trigonal (granular); Cleavage: none, breaks with conchoidal fracture; Specific gravity: 2.6-2.7.

Formation & Geological History

Formed through the regional metamorphism of quartz-rich sandstone. High heat and pressure cause the sand grains to recrystallize and fuse together. It can be found in mountain belts and Precambrian shields worldwide.

Uses & Applications

Used as a decorative stone in landscaping, as aggregate in road construction, and as a raw material for glass and ceramics. High-purity quartzite is used to produce silicon metal.

Geological Facts

Quartzite is so tough that it often outlasts the surrounding rocks, forming prominent ridges and weathered outcrops. It is significantly harder and more durable than the sandstone from which it originated.

Field Identification & Locations

Identify in the field by its granular, sugary texture and extreme hardness (it will easily scratch glass). Common in river beds as rounded cobbles and in mountainous regions. Look for its lack of reaction to acid, which distinguishes it from marble.

Identified on: 5/1/2026

Mode: Standard