sedimentary

Weathered limestone or chert-rich limestone

Calcitic limestone, primarily calcium carbonate (CaCO₃), possibly with microcrystalline silica and iron-oxide staining

AI-generated identification · may be incorrect

Hardness about 3 (limestone) to 6.5–7 where cherty patches occur; dull to weakly waxy luster, gray-beige color, opaque, and fine-grained with irregular weathering. It may fizz vigorously with dilute hydrochloric acid if calcitic, while silica-rich areas will not.

Identified September 15, 2026More sedimentary →

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At a glance

Common name: Weathered limestone or chert-rich limestone
Scientific name: Calcitic limestone, primarily calcium carbonate (CaCO₃), possibly with microcrystalline silica and iron-oxide staining
Category: sedimentary
Identified: September 15, 2026
Method: Standard

AI Estimated Value

Approximately $0–$5 as an ordinary found stone; $10–$30 if unusually attractive, fossiliferous, or polished.

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 from compacted marine carbonate mud or shell debris, later altered and weathered at the surface; iron oxides produce the yellow-brown patches. Exact age and locality cannot be determined from the photograph.

Uses & applications

Common limestone is used for aggregate, cement, lime, building stone, and soil treatment; attractive polished pieces may be collected as lapidary material, though this specimen appears ordinary.

Geological facts

The rounded shape and mottled surface are consistent with stream or beach abrasion and differential weathering. A conchoidal fracture and lack of acid reaction would support significant chert content.

Field identification & locations

Test an inconspicuous spot with dilute acid, check for scratches with a steel nail, and inspect a fresh break for fossils or glassy/conchoidal fracture. Similar stones occur widely in carbonate terrains, river gravels, and beaches.