metamorphic

Tumbled quartzite pebble

Quartzite, predominantly crystalline SiO₂

AI-generated identification · may be incorrect

Hardness about 7 Mohs; tan to honey-brown, fine-grained, opaque to slightly translucent, with a vitreous-to-waxy luster. Massive texture and conchoidal-to-irregular fracture; the smooth surface indicates tumbling or natural water wear.

Identified September 12, 2026More metamorphic →

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Physical properties

Formation & geological history

Formed when quartz-rich sandstone recrystallized under metamorphic heat and pressure, commonly during Precambrian to Paleozoic mountain-building. The rounded shape resulted from erosion or deliberate polishing.

Uses & applications

Used as durable aggregate, paving and decorative stone; attractive pieces may be sold as inexpensive lapidary or ornamental specimens.

Geological facts

Quartzite is generally harder and more resistant to weathering than its sandstone precursor. The tan color likely reflects iron-oxide staining or minor clay/iron-bearing impurities.

Field identification & locations

Identify it by its sugary quartz texture, lack of obvious cleavage, and inability to scratch glass only if the surface is uncoated; a steel knife should not scratch it. Common in glacial deposits, river gravels, and metamorphic mountain belts worldwide.