Quartzite

Physical Properties

Hardness: 7 on Mohs scale (scratches glass). Color: Often white, grey, or pinkish due to iron oxide. Luster: Vitreous to dull. Crystal structure: Non-foliated, interlocking mosaic of quartz crystals. Specific gravity: 2.6-2.7.

Formation & Geological History

Formed through the metamorphism of quartz sandstone. Intense heat and pressure from tectonic compression cause the original quartz grains to recrystallize and fuse together. Typically found in mountain belts (orogenic zones).

Uses & Applications

Used in construction as crushed stone for road ballast, as decorative stone in architecture, in the manufacture of glass, and occasionally as a semi-precious stone for lapidary work.

Geological Facts

Quartzite is so tough that it often survives erosion better than the surrounding rocks, forming prominent ridges and 'hogbacks' in the landscape. It is often confused with marble, but quartzite is much harder and will not react to acid.

Field Identification & Locations

Identify in the field by its extreme hardness, grainy 'sugary' texture on fresh breaks, and rounded shape if found in riverbeds (cobbles). It is found globally in ancient shield areas and folded mountain ranges.

Identified on: 4/25/2026

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