sedimentary

Tumbled brown chert or flint pebble

Microcrystalline quartz (SiO₂), commonly called chert; exact identification is uncertain from the image

AI-generated identification · may be incorrect

Very fine-grained, brown, opaque, and waxy-to-dull; quartz hardness about 7 Mohs, conchoidal fracture, no visible cleavage, and specific gravity about 2.6. The rounded cylindrical shape appears naturally water-worn or deliberately tumbled.

Identified August 16, 2026More sedimentary →

Explore Tumbled brown chert or flint pebble in the encyclopedia →

Identify your own rocks.

Get a report just like this from any photo, free.

App Store Google Play

Physical properties

Formation & geological history

Chert forms when silica from organisms or groundwater replaces and cements sediment, often in limestone or marine beds; ages range from Precambrian to recent. It commonly occurs as nodules, beds, or stream pebbles.

Uses & applications

Used historically for cutting tools and fire-starting; attractive pieces are collected or used decoratively. It has little value unless unusually patterned, colorful, or proven archaeological.

Geological facts

Its dark, fine-grained fracture and waxy surface distinguish it from coarse sandstone. Brown coloration commonly comes from iron oxides or hydroxides.

Field identification & locations

Look for a glassy conchoidal fracture, uniform microtexture, and inability to scratch it with a steel knife; it should scratch ordinary glass. Common in limestone regions and gravel deposits worldwide.