sedimentary

Weathered iron-rich limestone or calcareous sandstone

Calcite-rich carbonate rock, possibly ferruginous limestone (CaCO₃ with iron oxides)

AI-generated identification · may be incorrect

Tan to rusty-brown, very rough and porous, with dull earthy luster and apparent granular texture. Likely hardness 3–4; calcite-rich areas should fizz with dilute hydrochloric acid or vinegar, while iron oxides cause the ochre coloration.

Identified September 6, 2026More sedimentary →

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At a glance

Common name: Weathered iron-rich limestone or calcareous sandstone
Scientific name: Calcite-rich carbonate rock, possibly ferruginous limestone (CaCO₃ with iron oxides)
Category: sedimentary
Identified: September 6, 2026
Method: Standard

AI Estimated Value

Usually $1–$10 as an unremarkable hand specimen; up to about $20–$50 if locality-specific, fossiliferous, or unusually attractive.

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

Formed from deposited carbonate sediment or carbonate-cemented sand, later altered by groundwater weathering and oxidation. Its precise age cannot be determined from the photograph; such rocks range from Paleozoic to Cenozoic.

Uses & applications

Used locally as aggregate, road stone, fill, or building stone; attractive weathered pieces may be kept as geological specimens, but it is not typically a jewelry material.

Geological facts

The rusty color commonly comes from hematite and goethite coating or replacing calcite. Strongly irregular cavities may reflect dissolution of fossils, shells, or carbonate cement.

Field identification & locations

Common in sedimentary terrains worldwide, especially limestone belts and arid weathering zones. Field identification requires an acid test, streak, and a fresh broken surface; the image alone cannot distinguish limestone from calcareous sandstone confidently.