metamorphic

Quartzite Pebble

Quartzite

AI-generated identification · may be incorrect

Hardness: 7 (Mohs scale); Color: Grayish-green with white translucent spots; Luster: Vitreous to dull; Crystal structure: Non-foliated, granular; Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.7

Hardness: 7 (Mohs scale)
Color: Grayish-green with white translucent spots
Luster: Vitreous to dull

Identified July 14, 2026More metamorphic →

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Physical properties

Formation & geological history

Formed from the metamorphism of quartz-rich sandstone under extreme heat and pressure, causing the original quartz grains to recrystallize and fuse together. This specimen appears water-worn and rounded by fluvial or glacial transport.

Uses & applications

Used in construction as crushed stone, for road ballast, as a refractory material in glass making, and sometimes polished for decorative purposes or landscaping.

Geological facts

Quartzite is so tough that it often remains as resistant ridges or 'monadnocks' long after softer surrounding rocks have eroded away. It is often confused with marble but will not react with acid.

Field identification & locations

To identify in the field, look for a rock that is harder than glass and has a 'sugary' texture on fresh breaks. This rounded cobble form is common in riverbeds, glacial tills, and along coastal beaches globally.