Quartzite

Physical Properties

Hardness: 7 on Mohs scale; Color: White to grey, sometimes reddish or tan due to impurities; Luster: Vitreous to dull; Crystal structure: Hexagonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.7

Formation & Geological History

Formed when quartz-rich sandstone is subjected to high heat and pressure during regional metamorphism, causing the quartz grains to recrystallize and fuse together. It can be found in mountain belts and Precambrian shields worldwide.

Uses & Applications

Used in construction as crushed stone or decorative building stone (veneers), road ballast, manufacturing of glass and ceramics, and as a raw material for silicon production.

Geological Facts

Quartzite is so tough that it often survives intense weathering and erosion longer than surrounding rocks, forming prominent ridges and peaks. It was used by early humans for making stone tools when flint was unavailable.

Field Identification & Locations

Identify it by its extreme hardness (it will easily scratch glass) and its grainy, sandpaper-like texture that lacks the visible pores of sandstone. It is common in riverbeds and mountainous regions like the Appalachians or the Alps.

Identified on: 5/1/2026

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