sedimentary

Weathered iron-rich limestone or carbonate rock

Calcitic limestone, possibly limonite/goethite-stained; exact identification requires testing

AI-generated identification · may be incorrect

Likely pale gray to tan calcite with rusty brown iron-oxide coatings and a rough, vuggy texture; calcite hardness ~3, vitreous to earthy luster, rhombohedral cleavage, and specific gravity ~2.7. Effervesces with dilute hydrochloric acid if calcitic, though the image alone cannot confirm composition.

Identified September 12, 2026More sedimentary →

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At a glance

Common name: Weathered iron-rich limestone or carbonate rock
Scientific name: Calcitic limestone, possibly limonite/goethite-stained; exact identification requires testing
Category: sedimentary
Identified: September 12, 2026
Method: Standard

AI Estimated Value

Typically $1-$10 as a common hand specimen; generally under $20 unless locality, fossil content, or unusual mineralization is documented.

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

Probably formed as marine or freshwater carbonate sediment that lithified, then underwent weathering and iron-oxide staining; age and depositional setting cannot be determined visually.

Uses & applications

Limestone is used for aggregate, cement, lime, and building stone; attractive iron-stained pieces may be kept as teaching or display specimens, but this fragment has little commercial value.

Geological facts

The brown coloration commonly comes from limonite or goethite, hydrated iron-oxide minerals produced during oxidation and weathering.

Field identification & locations

Common in carbonate terrains worldwide. Test with a steel nail, dilute acid, and streak examination; strong fizzing indicates calcite-rich limestone, while no fizz may indicate silica-rich rock or heavy surface alteration.