sedimentary

Porous limestone (likely reef or shell limestone)

Calcium-carbonate rock, predominantly calcite (CaCO₃); possibly bioclastic limestone or coquina

AI-generated identification · may be incorrect

Very light gray to cream, highly porous and rough with abundant cavities; dull to earthy luster, typically massive and non-crystalline. Calcite hardness is about Mohs 3; it commonly fizzes vigorously with dilute hydrochloric acid or vinegar.

Identified September 16, 2026More sedimentary →

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At a glance

Common name: Porous limestone (likely reef or shell limestone)
Scientific name: Calcium-carbonate rock, predominantly calcite (CaCO₃); possibly bioclastic limestone or coquina
Category: sedimentary
Identified: September 16, 2026
Method: Standard

AI Estimated Value

Typically $5–$30 for a hand specimen; larger attractive fossiliferous or architectural pieces may sell for $50–$200.

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

Forms from accumulated shells, coral, and carbonate mud in shallow marine environments, later lithified and often altered by dissolution. Exact geological age cannot be determined from the image; such limestone ranges from Paleozoic to modern deposits.

Uses & applications

Used as building stone, aggregate, cement and lime feedstock, landscaping rock, and soil conditioner; attractive pieces may be used decoratively. Porous varieties are generally low-value as specimens.

Geological facts

The cavities commonly reflect dissolved shells, coral pores, or weathered fossil structures. Limestone is dominated by calcite, unlike dolostone, which is chiefly dolomite.

Field identification & locations

Common in Florida, the Caribbean, Mediterranean, coastal Australia, and many former reef environments. Identify it by its pale color, low hardness, visible fossil/void textures, and acid reaction; avoid confusing it with concrete or volcanic pumice.