sedimentary

Tumbled fossiliferous limestone

Bioclastic limestone, primarily calcite (CaCO₃)

AI-generated identification · may be incorrect

Cream-to-gray rounded pebble with visible fossil fragments or shell cross-sections in a fine calcite-rich matrix; Mohs hardness 3, dull to subtly waxy luster, nonfoliated, and commonly reacts vigorously with dilute hydrochloric acid or vinegar.

Identified August 23, 2026More sedimentary →

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Physical properties

Formation & geological history

Forms from accumulated marine shell and skeletal debris that lithifies by compaction and cementation, commonly during Paleozoic–Mesozoic marine deposition; the rounded shape indicates later stream, beach, or human tumbling abrasion.

Uses & applications

Used as aggregate, cement and lime feedstock, decorative stone, landscaping material, and educational or lapidary specimens; modest jewelry use when polished.

Geological facts

The prominent circular features may be fossil shells, crinoid fragments, or other bioclasts, but the photograph alone cannot determine the exact fossil. Acid effervescence is the most useful confirmation of calcitic limestone.

Field identification & locations

Common in former shallow-marine sedimentary basins worldwide, including the United States, Europe, and Asia; inspect with a hand lens for shell walls, chambers, or crinoid segmentation and test an inconspicuous area with acid.