fossil

Fossiliferous limestone (likely orthoceras or crinoid-bearing limestone)

Bioclastic carbonate rock; commonly calcite (CaCO₃) with fossil fragments

AI-generated identification · may be incorrect

Dark gray to black, polished surface with abundant pale fossil cross-sections; calcite has Mohs hardness 3, vitreous to dull luster, and rhombohedral cleavage. Effervesces with dilute hydrochloric acid, though polishing may obscure the reaction.

Identified August 20, 2026More fossil →

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Physical properties

Formation & geological history

Formed when marine shells or skeletal debris accumulated, were buried, lithified, and later polished; fossil-bearing limestones commonly range from Paleozoic to Mesozoic age. The elongated white fragments may be orthocone cephalopods or crinoid stems.

Uses & applications

Used for ornamental stone, bookends, cabochons, and decorative carvings; generally not suited to heavy construction because calcite is relatively soft and acid-sensitive.

Geological facts

The fossils are preserved as calcite-rich infill or replacement within the limestone matrix. A polished surface can make fossil-rich material resemble patterned marble.

Field identification & locations

Identify by the repeated fossil shapes, calcite hardness, and acid fizz; inspect an unpolished edge with a hand lens and test cautiously. Common commercial sources include Morocco, Madagascar, and China.