sedimentary
Fossiliferous Limestone
Calcium Carbonate (CaCO3) with Bioclasts
Hardness: 3 (Mohs); Color: Grey, tan, off-white; Luster: Dull to earthy; Crystal structure: Trigonal (microcrystalline calcite matrix); Cleavage: None/clastic; Specific Gravity: 2.5-2.7
- Hardness
- 3 (Mohs)
- Color
- Grey, tan, off-white
- Luster
- Dull to earthy
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Physical properties
Hardness: 3 (Mohs); Color: Grey, tan, off-white; Luster: Dull to earthy; Crystal structure: Trigonal (microcrystalline calcite matrix); Cleavage: None/clastic; Specific Gravity: 2.5-2.7
Formation & geological history
Formed in shallow, warm marine environments through the accumulation of shell, coral, and algal debris. The pressure of overlying sediment causes lithification over millions of years, often dating from the Paleozoic to Mesozoic eras.
Uses & applications
Used primarily in the construction industry as crushed stone, in the manufacture of cement, and as a soil conditioner (aglime) to neutralize acidity.
Geological facts
Many limestones are composed almost entirely of biological remains. This specific specimen shows 'vugs' or cavities where organic material has weathered out or where minerals have begun to precipitate.
Field identification & locations
Identify in the field by its gray weathered surface and the presence of visible fossils or shell fragments. It will react and fizz (effervesce) when a drop of diluted hydrochloric acid is applied.
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