fossil

Likely fossilized coral or porous limestone fragment

Calcite (CaCO₃), possibly fossil coral such as Scleractinia; exact identification requires microscopy

AI-generated identification · may be incorrect

Gray-white, weathered, and highly porous with a rough granular surface; likely Mohs hardness 3, vitreous to dull luster, and calcite’s rhombohedral cleavage. The cavity texture may show fossilized coral or shell structure rather than crystalline rock.

Identified August 22, 2026More fossil →

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At a glance

Common name: Likely fossilized coral or porous limestone fragment
Scientific name: Calcite (CaCO₃), possibly fossil coral such as Scleractinia; exact identification requires microscopy
Category: fossil
Identified: August 22, 2026
Method: Standard

AI Estimated Value

About $5–$25 as an ordinary fragment; $30–$100+ if confirmed, attractive, and locality-documented fossil coral.

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 a marine carbonate deposit, later lithified and weathered; if coral, the original skeleton was aragonite or calcite and may be Paleozoic to Cenozoic in age. The image alone cannot establish age or locality.

Uses & applications

Primarily a collectible or teaching specimen; carbonate rock may be used for aggregate, cement, and lime, while fossil coral is not generally used industrially.

Geological facts

Calcite-rich material commonly reacts vigorously with dilute hydrochloric acid or household vinegar, especially when powdered. Fossil coral typically displays repeated polygonal corallite cells under magnification.

Field identification & locations

Inspect the broken end with a hand lens for regular coral cups, shell layers, or sediment grains; perform an acid test only on an inconspicuous spot. Common sources include marine limestone regions worldwide.