Quartzite

Physical Properties

Hardness: 7 on Mohs scale. Color: White, gray, or tan. Luster: Vitreous to dull. Crystal structure: Non-foliated, granular. Cleavage: None (fractures across grains). Specific gravity: 2.6-2.7.

Formation & Geological History

Formed from the metamorphism of quartz sandstone under intense heat and pressure. Most specimens are from the Proterozoic or Paleozoic eras. It typically forms in orogenic (mountain-building) zones.

Uses & Applications

Used in construction as crushed stone for road ballast, as decorative stone in landscaping, and in floors and countertops. Historically used for making stone tools due to its hardness and durability.

Geological Facts

Quartzite is so tough that it often outlasts the surrounding rock, forming high ridges and resistant mountains. It is more durable than granite and can withstand chemical weathering very well.

Field Identification & Locations

Identify by its ability to scratch glass and its granular, crystalline texture. Unlike sandstone, quartzite breaks through the quartz grains rather than around them. Found globally in mountainous regions and riverbeds.

Identified on: 4/22/2026

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