metamorphic

Tumbled gray quartzite or quartz-rich river pebble

Quartzite; predominantly microcrystalline quartz (SiO₂), possibly with minor feldspar or mica

AI-generated identification · may be incorrect

Hardness about 7 Mohs; smooth, rounded, gray-beige surface with a subdued waxy to vitreous luster. Massive, nonfoliated texture and no obvious cleavage; specific gravity approximately 2.6–2.7.

Identified September 21, 2026More metamorphic →

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Physical properties

Hardness about 7 Mohs; smooth, rounded, gray-beige surface with a subdued waxy to vitreous luster. Massive, nonfoliated texture and no obvious cleavage; specific gravity approximately 2.6–2.7.

Formation & geological history

Quartzite forms when quartz-rich sandstone is metamorphosed under heat and pressure, commonly during mountain building; its precise age cannot be determined from the photograph. The rounded shape indicates later river or beach abrasion, followed by tumbling or polishing.

Uses & applications

Used as crushed stone, aggregate, paving, decorative stone, and occasionally as a lapidary or ornamental specimen. This piece has modest value unless its pattern or provenance is exceptional.

Geological facts

Quartzite is typically harder and more resistant to weathering than its sandstone precursor. The specimen may also be a quartz-rich chert or silicified pebble, which cannot be distinguished confidently from the image alone.

Field identification & locations

Look for a sugary quartz texture, lack of layering, and inability to scratch with a steel knife; quartz should scratch glass. Common in metamorphic mountain belts and gravel deposits worldwide; acid testing is generally unhelpful.