Quartzite

Physical Properties

Hardness: 7 on Mohs scale (harder than glass). Color: Grey, white, or yellowish-tan. Luster: Vitreous to dull. Structure: Granoblastic, non-foliated. Cleavage: None (conchoidal fracture). Specific Gravity: 2.6 to 2.7.

Formation & Geological History

Formed through the regional or contact metamorphism of quartzose sandstone. Under intense heat and pressure, quartz grains recrystallize and fuse together. Generally found in Precambrian to Paleozoic mountain belts.

Uses & Applications

Used as crushed stone for road construction and railway ballast; also used as a decorative stone in architecture, countertops, and flooring due to its durability and resemblance to marble.

Geological Facts

Quartzite is so tough that it often outlasts the surrounding rocks; it frequently forms the caps of ridges and mountain peaks. Unlike sandstone, when broken, quartzite fractures through the quartz grains rather than around them.

Field Identification & Locations

Identify in the field by its hardness (it will easily scratch a knife blade or glass plate) and its sugary, crystalline texture. It is often found in riverbeds as rounded cobbles or on mountainous outcrops.

Identified on: 4/27/2026

Mode: Standard