sedimentary

Weathered limestone

Limestone; predominantly calcite (CaCO₃)

AI-generated identification · may be incorrect

Tan, earthy, fine- to coarse-grained, with irregular fractures and possible fossil or recrystallized textures; calcite has Mohs hardness 3, vitreous to dull luster, and rhombohedral cleavage. It should effervesce noticeably in dilute hydrochloric acid or vinegar if fresh calcite is exposed.

Identified August 28, 2026More sedimentary →

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Physical properties

Formation & geological history

A carbonate sedimentary rock formed mainly from accumulated marine shells, lime mud, or chemical precipitation, commonly during Paleozoic–Cenozoic marine deposition; surface weathering has produced the rough brown exterior.

Uses & applications

Used for aggregate, cement and lime manufacture, building stone, and soil amendment; attractive pieces may be kept as low-cost geological specimens.

Geological facts

Limestone commonly contains fossils, though none are clearly diagnostic in this small specimen. Dissolution of limestone forms karst landscapes, caves, and sinkholes.

Field identification & locations

Common worldwide, especially in former shallow seas; inspect for visible fossils, grain texture, and acid reaction, while distinguishing it from nonreactive sandstone or quartzite. Typical value is $1–$10 for an ordinary hand specimen, or $10–$30 if fossiliferous or unusually textured.