sedimentary

Limestone (containing Fossil Mold)

Sedimentary Calcium Carbonate (CaCO3)

AI-generated identification · may be incorrect

Hardness: 3 on Mohs scale; Color: Tan, beige, or off-white; Luster: Dull or earthy; Structure: Microcrystalline to clastic; Cleavage: None (fractures irregularly).

Hardness: 3 on Mohs scale
Color: Tan, beige, or off-white
Luster: Dull or earthy

Identified June 14, 2026More sedimentary →

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Physical properties

Hardness: 3 on Mohs scale; Color: Tan, beige, or off-white; Luster: Dull or earthy; Structure: Microcrystalline to clastic; Cleavage: None (fractures irregularly).

Formation & geological history

Formed in clear, warm, shallow marine waters from the accumulation of shell, coral, algal, and fecal debris. This specific specimen appears to contain a mold or impression of a prehistoric marine organism, potentially Paleozoic or Mesozoic in age.

Uses & applications

Limestone is used extensively in construction (aggregate, cement), agriculture (soil treatment), and industrial manufacturing (glass making, iron smelting).

Geological facts

Over 10% of all sedimentary rocks are limestones. They often contain macrofossils that provide a snapshot of ancient marine ecosystems. This specimen shows a 'negative' impression or mold of an organic structure.

Field identification & locations

Identify in the field by checking if it fizzes when exposed to a weak acid (like vinegar). Look for evidence of biological remains or shell fragments. Commonly found in areas that were once prehistoric seafloors.