sedimentary
Fossiliferous Limestone (Gritstone/Marl)
CaCO3 (Calcium Carbonate) with Fossil Inclusions
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
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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.
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