sedimentary
Fossiliferous Limestone
Biogenic Limestone (Calcium Carbonate, CaCO3)
Hardness: 3 (Mohs scale); Color: Cream, grey, or tan; Luster: Dull to earthy; Crystal structure: Non-crystalline matrix with skeletal fragments; Cleavage: None (conchoidal or irregular fracture); Specific gravity: 2.3-2.7
- Hardness
- 3 (Mohs scale)
- Color
- Cream, grey, or tan
- Luster
- Dull to earthy
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Physical properties
Hardness: 3 (Mohs scale); Color: Cream, grey, or tan; Luster: Dull to earthy; Crystal structure: Non-crystalline matrix with skeletal fragments; Cleavage: None (conchoidal or irregular fracture); Specific gravity: 2.3-2.7
Formation & geological history
Formed in marine environments through the accumulation of shell, coral, algal, and fecal debris. These organic remains are lithified over millions of years by pressure and mineral precipitation, typically in shallow tropical waters.
Uses & applications
Used in the manufacturing of cement, as a soil conditioner in agriculture, a building material, and as crushed stone for road bases. Well-preserved specimens are used for educational purposes and fossil collections.
Geological facts
Limestone makes up about 10% of the total volume of all sedimentary rocks. It often preserves entire ancient ecosystems, providing a 'snapshot' of the ocean floor from hundreds of millions of years ago.
Field identification & locations
Identify by looking for visible shell fragments or skeletal structures embedded in a fine-grained matrix. It will react and fizz (effervesce) when exposed to a weak acid like vinegar due to its calcium carbonate content.
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