Quartzite

Physical Properties

Hardness: 7 (Mohs scale), Color: tan, yellow, orange (due to iron oxidation), white or grey, Luster: vitreous to dull, Crystal structure: Trigonal (microcrystalline), Specific gravity: 2.6-2.7

Formation & Geological History

Formed from the metamorphism of quartz sandstone under intense heat and pressure, typically during mountain-building events. This specimen shows water-worn rounding and iron staining.

Uses & Applications

Used in construction as road ballast, railway ballast, and decorative stone. Historically used for making stone tools due to its hardness and conchoidal fracture.

Geological Facts

Quartzite is so tough that it often outlasts the surrounding rocks during erosion, forming prominent ridges and hills. It is harder than a steel knife and will easily scratch glass.

Field Identification & Locations

Identify by its extreme hardness and grainy texture that looks like sandpaper but is smooth to the touch. Look for it in riverbeds or glacial tills where resistant rocks accumulate.

Identified on: 5/2/2026

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