sedimentary

Fossiliferous limestone, likely containing a large bivalve or gastropod fossil

Calcite-rich limestone (CaCO₃) with molluscan bioclast

AI-generated identification · may be incorrect

Typically Mohs hardness 3, gray to tan, earthy to dull luster, fine-to-medium crystalline calcite matrix, and weak to indistinct cleavage; reacts vigorously with dilute hydrochloric acid. The darker areas may include clay, iron oxides, or carbonaceous material.

Identified September 12, 2026More sedimentary →

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Physical properties

Formation & geological history

Forms from accumulated marine carbonate sediment later lithified and locally recrystallized; the embedded shell likely dates from the Paleozoic to Cenozoic, depending on locality. Exact age cannot be determined from the photograph alone.

Uses & applications

Used as aggregate, cement and lime feedstock, building stone, and ornamental material; fossiliferous pieces are collected for display and education.

Geological facts

Molluscan shells are commonly preserved as molds, casts, or partially replaced calcite fossils within limestone.

Field identification & locations

Look for visible shell symmetry, layered or coiled structures, a sugary calcite texture, and acid effervescence; common in former shallow-marine sedimentary basins worldwide. Avoid acid testing if preservation or value matters.