sedimentary

Likely gray chert (flint) pebble

Microcrystalline quartz (SiO₂), commonly called chert or flint

AI-generated identification · may be incorrect

Opaque gray-brown, dull to waxy surface, with no visible crystals; hardness about 6.5–7 Mohs and conchoidal fracture. The elongated shape may be naturally worn or shaped, but the image alone cannot confirm either.

Identified October 13, 2026More sedimentary →

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Physical properties

Formation & geological history

Chert forms when silica accumulates and recrystallizes in sedimentary rocks, often from microscopic organisms; it occurs across many geological ages. This specimen’s specific age and formation setting cannot be determined from the photo.

Uses & applications

Chert has been used historically for sharp-edged tools and, when suitable, as a source of silica; ordinary pebbles are mainly collected or decorative.

Geological facts

A fresh broken surface typically shows smooth, curved conchoidal fractures and sharp edges.

Field identification & locations

Look for a dense, fine-grained texture, lack of visible grains, and conchoidal fracture; common in sedimentary regions worldwide. The specimen is too indistinct to identify more specifically from the photo.