sedimentary

Weathered brown chert or silicified mudstone

Microcrystalline quartz (chalcedony), SiO₂; possibly a ferruginous silicified sediment

AI-generated identification · may be incorrect

Hardness about 6.5–7 Mohs, brown to ochre with iron-oxide staining, dull to waxy luster, very fine-grained and massive, with irregular conchoidal-like fractures and no visible cleavage. The smooth rounded shape indicates natural abrasion or tumbling.

Identified September 17, 2026More sedimentary →

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At a glance

Common name: Weathered brown chert or silicified mudstone
Scientific name: Microcrystalline quartz (chalcedony), SiO₂; possibly a ferruginous silicified sediment
Category: sedimentary
Identified: September 17, 2026
Method: Standard

AI Estimated Value

Approximately $1–$15 as a common hand specimen; up to $20–$50 if it has unusual patterns, provenance, or fossil content.

Not an official valuation

AI estimate for general interest only — not an appraisal. Actual value depends on condition, provenance, and market demand. Verify with a professional before buying, selling, or insuring.

This identification was generated by AI and may contain errors. Verify important details before relying on them — and never use an AI result to judge whether a specimen is safe to handle. Read the full disclaimer

Physical properties

Formation & geological history

Likely formed when silica replaced or cemented fine sediment, followed by weathering and transport; exact age cannot be determined from the photograph. Chert occurs in sedimentary sequences from Precambrian to recent geological ages.

Uses & applications

Used historically for sharp-edged tools and occasionally as aggregate or decorative stone; attractive pieces may be collected, but this specimen has limited commercial value.

Geological facts

Chert commonly preserves fossils or subtle bedding, while iron oxides produce the yellow-brown coloration. A fresh broken surface would typically appear darker, smoother, and slightly waxy.

Field identification & locations

Common in limestone and other sedimentary terrains, including the Midwest, Texas, western United States, and many river gravels worldwide. Confirm with a hardness test: it should scratch ordinary glass, unlike most mudstone; avoid destructive testing on valuable specimens.