sedimentary

Chert (likely flint), possibly chalcedony-rich

Microcrystalline quartz, SiO₂ (quartz/chalcedony)

AI-generated identification · may be incorrect

Hardness about 7 Mohs; brown, tan, gray, and translucent areas with a waxy to dull luster. It is massive rather than visibly crystalline, lacks cleavage, and commonly shows conchoidal fracture; the pale rough coating may be weathered cortex or quartz-rich alteration.

Identified August 28, 2026More sedimentary →

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Physical properties

Formation & geological history

Chert forms when silica replaces carbonate sediments or accumulates from siliceous biological material, usually during diagenesis. Its exact geological age cannot be determined from the photograph; chert occurs from Precambrian to recent formations.

Uses & applications

Used historically for sharp-edged tools and fire-starting, and today as aggregate, road material, and a lapidary material. Attractive pieces may be polished for display, though this specimen appears primarily a common field find.

Geological facts

The sharp, curved fractures and glassy translucent interior are characteristic of chert/flint. Brown coloration can result from iron oxides or organic impurities.

Field identification & locations

Identify it by its very hard, nonporous body, waxy appearance, and conchoidal edges; it should scratch ordinary glass. Common in limestone, chalk, and gravel deposits worldwide, especially flint-bearing regions.