sedimentary

Rounded brown pebble, likely chert or iron-stained quartzite

Chert (microcrystalline quartz, SiO₂) or quartzite (recrystallized quartz, SiO₂)

AI-generated identification · may be incorrect

Dark reddish-brown, opaque, smooth and rounded with a dull to slightly waxy luster; likely hardness 6.5–7 Mohs, with no visible cleavage. The small size and surface wear indicate water transport or tumbling.

Identified August 8, 2026More sedimentary →

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Physical properties

Formation & geological history

If chert, it formed from silica-rich sediment or biological silica that lithified and recrystallized; if quartzite, it formed when sandstone was metamorphosed. The specimen’s exact geological age and origin cannot be determined from the image.

Uses & applications

Commonly collected as a pebble or used for lapidary work; chert can produce sharp edges when fractured, while quartzite is used as aggregate, building stone, and sometimes jewelry material.

Geological facts

Chert often has a waxy luster and conchoidal fracture; quartzite typically shows a sugary, crystalline texture. A steel file should not easily scratch either material.

Field identification & locations

Common in streambeds, gravel deposits, and glacial sediments worldwide. Identification requires a scratch test, streak test, and close inspection of fracture and grain texture.