Quartzite

Physical Properties

Hardness: 7 on Mohs scale. Color: Grayish-white to yellowish-brown with translucent areas. Luster: Vitreous to dull. Crystal structure: Hexagonal (though usually granular/massive). Cleavage: None (conchoidal fracture). 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. Often found in Precambrian and Paleozoic rock formations.

Uses & Applications

Used in construction as crushed stone or decorative facing, in metallurgy as a source of silica, and as a durable material for countertops and flooring.

Geological Facts

Quartzite is so hard and chemically resistant that it often forms the caprock or spine of mountain ranges. It is harder than steel and will easily scratch glass.

Field Identification & Locations

Identify in the field by its extreme hardness and the fact that it breaks across the original sand grains rather than around them. Commonly found in riverbeds as rounded cobbles like this specimen.

Identified on: 4/27/2026

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