sedimentary

Likely chert (flint) pebble

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

AI-generated identification · may be incorrect

Dull gray-tan, rounded pebble with a fine-grained appearance and pale fractured area. Quartz hardness is about 7 Mohs; it has no visible cleavage and a waxy-to-dull luster on weathered surfaces.

Identified October 10, 2026More sedimentary →

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Physical properties

Dull gray-tan, rounded pebble with a fine-grained appearance and pale fractured area. Quartz hardness is about 7 Mohs; it has no visible cleavage and a waxy-to-dull luster on weathered surfaces.

Formation & geological history

Chert forms when silica precipitates or replaces sediment, often in marine settings, and can occur in sedimentary layers of many geological ages. The rounded shape suggests transport and abrasion in a stream or on a shore.

Uses & applications

Chert has historically been used for tools and fire-starting; attractive pieces may be collected or used in crafts. This small, ordinary pebble has little commercial value.

Geological facts

Chert commonly breaks with a curved, shell-like (conchoidal) fracture and sharp edges. The pale patch may be a fresh fracture or a lighter inclusion.

Field identification & locations

Look for very fine texture, hardness sufficient to scratch glass, and conchoidal fracture; these features help distinguish chert from softer rocks. Chert occurs worldwide in sedimentary formations and river or beach gravels.