sedimentary

Weathered limestone fragment

Limestone, predominantly calcite (CaCO₃), possibly fossiliferous or dolomitic

AI-generated identification · may be incorrect

Soft, pale cream-gray, earthy to dull luster, fine-grained and irregularly fractured; Mohs hardness about 3, with possible weak effervescence in dilute hydrochloric acid. Crystal structure is generally microscopic calcite; cleavage is not usually visible in the specimen.

Identified September 4, 2026More sedimentary →

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Physical properties

Formation & geological history

Forms from accumulated carbonate mud, shells, or chemical precipitation in marine or freshwater settings, commonly during the Paleozoic–Mesozoic eras. Surface weathering has rounded and stained this fragment.

Uses & applications

Used extensively for cement, aggregate, roadstone, agricultural lime, and building stone; attractive fossiliferous varieties are collected or cut for décor. This small weathered piece has little commercial value.

Geological facts

Limestone commonly dissolves to form caves, sinkholes, and karst landscapes. Acid fizzing strongly supports calcite-rich limestone, while little or no fizz may indicate dolomite or a noncarbonate rock.

Field identification & locations

Common worldwide, especially in former shallow tropical seas; major occurrences include the United States, Europe, China, and the Caribbean. Test a fresh surface with vinegar or dilute acid, inspect for fossils, and compare its softness with glass or steel.