sedimentary

Fossiliferous Limestone (Gritstone/Marl)

CaCO3 (Calcium Carbonate) with Fossil Inclusions

AI-generated identification · may be incorrect

Hardness: 3-4 (Mohs scale); Color: Tan, beige, or yellowish-white; Luster: Dull to earthy; Structure: Fine-grained matrix with visible biological inclusions; Specific Gravity: 2.5-2.7.

Hardness: 3-4 (Mohs scale)
Color: Tan, beige, or yellowish-white
Luster: Dull to earthy

Identified March 23, 2026More sedimentary →

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Physical properties

Hardness: 3-4 (Mohs scale); Color: Tan, beige, or yellowish-white; Luster: Dull to earthy; Structure: Fine-grained matrix with visible biological inclusions; Specific Gravity: 2.5-2.7.

Formation & geological history

Formed in shallow marine environments or riverbeds where organic debris, such as mollusk shells or coral fragments, accumulated and were cemented together by calcium carbonate over millions of years (likely Cenozoic or Mesozoic era).

Uses & applications

Primarily used as a construction aggregate, in the production of lime and cement, and occasionally as a decorative landscape stone. Unique specimens are kept by hobbyist fossil collectors.

Geological facts

This specimen shows 'shell hash' or coquina-like characteristics, meaning it contains fragments of ancient marine life that died and was buried in sediment before lithification.

Field identification & locations

Identify in the field by looking for visible shell fragments or small curved patterns within the stone. It will react and fizz if a drop of vinegar (weak acid) is applied, indicating the presence of calcite. Common in limestone-rich regions like Texas, the Midwest US, or coastal areas.