sedimentary
Limestone (containing Fossil Mold)
Sedimentary Calcium Carbonate (CaCO3)
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
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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.
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