sedimentary

Weathered limestone or calcareous rock

Calcite-rich limestone (predominantly CaCO₃), possibly fossiliferous

AI-generated identification · may be incorrect

Tan to yellow-brown, earthy to dull luster, irregular granular texture, and apparent porous/weathered surfaces; calcite hardness is Mohs 3, with good rhombohedral cleavage and specific gravity about 2.7. Exact identification is limited by the photograph.

Identified August 14, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed from compacted marine carbonate mud, shell debris, or chemical precipitation, commonly during Paleozoic–Cenozoic sedimentary deposition. Weathering and iron staining produce the yellow-brown coloration.

Uses & applications

Used as crushed aggregate, cement and lime feedstock, building stone, and occasionally as a fossil-bearing or decorative specimen; this fragment appears of low commercial grade.

Geological facts

Calcite-rich limestone effervesces vigorously with dilute hydrochloric acid or household vinegar, especially on a freshly scratched surface. Iron oxides commonly create tan, orange, or brown staining.

Field identification & locations

Common worldwide in former shallow marine basins, including the United States, Europe, and parts of Asia. Identify it by its relatively soft surface, carbonate reaction, and lack of visible interlocking crystals; distinguish it from sandstone by the acid test and finer carbonate texture.