sedimentary

Weathered porous limestone

Calcite-rich limestone (CaCO₃), possibly fossiliferous or dolomitic

AI-generated identification · may be incorrect

Tan-brown, earthy to dull luster, irregularly porous and vuggy texture; calcite hardness is about Mohs 3, with poor visible crystal structure and indistinct cleavage. It should fizz with dilute hydrochloric acid or strong vinegar, especially on a freshly scratched surface.

Identified September 21, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed from compacted carbonate mud, shells, or chemical precipitates in a marine or freshwater setting, then altered by weathering and dissolution. Its exact geological age cannot be determined from the image.

Uses & applications

Common limestone is used for cement, aggregate, lime, building stone, and soil treatment; attractive pieces may be collected as decorative specimens. This rough example has little jewelry value.

Geological facts

The holes likely reflect dissolved fossils, shell fragments, or weathering along natural pores and fractures. Dolomitization could reduce or eliminate the acid reaction, so testing a fresh surface is useful.

Field identification & locations

Common worldwide, especially in former shallow seas and karst regions; major deposits occur in the United States, Europe, and Southeast Asia. Distinguish it from sandstone by its softer calcite matrix and acid reaction.