sedimentary

Weathered fossiliferous limestone

Calcitic limestone, primarily CaCO₃; possible bioclastic fossil limestone

AI-generated identification · may be incorrect

Gray to tan, fine- to medium-grained, dull to faintly earthy luster, with rusty weathering and probable fossil or solution markings. Hardness is typically 3–4 Mohs; calcite has rhombohedral cleavage and reacts vigorously with dilute hydrochloric acid.

Identified September 14, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed from compacted and cemented marine carbonate mud and shell fragments, commonly during Paleozoic–Mesozoic shallow-sea deposition; exact age cannot be determined from the image.

Uses & applications

Used as aggregate, cement and lime feedstock, building stone, and landscaping material; attractive fossil-bearing pieces may be collected, but this specimen appears common and unpolished.

Geological facts

Limestone commonly preserves fossils and develops cavities or etched surfaces as groundwater dissolves calcite. Rust-colored patches are likely iron-oxide staining rather than native coloration.

Field identification & locations

Test a fresh surface with vinegar or dilute HCl for fizzing, and inspect with a hand lens for shell or skeletal fragments; common worldwide in former marine basins. Estimated value: $1–$15 as a common field specimen, potentially $20–$75 if clearly fossiliferous and well preserved.