sedimentary
Limestone
Calcium Carbonate (CaCO3)
Hardness: 3-4 (Mohs scale); Color: Dark gray to black; Luster: Dull to earthy; Crystal Structure: Microcrystalline calcite; Cleavage: None (conchoidal to irregular fracture); Specific Gravity: 2.3-2.7
- Hardness
- 3-4 (Mohs scale)
- Color
- Dark gray to black
- Luster
- Dull to earthy
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Physical properties
Hardness: 3-4 (Mohs scale); Color: Dark gray to black; Luster: Dull to earthy; Crystal Structure: Microcrystalline calcite; Cleavage: None (conchoidal to irregular fracture); Specific Gravity: 2.3-2.7
Formation & geological history
Formed through the accumulation of shell, coral, algal, and fecal debris in marine environments; age varies from Precambrian to Holocene.
Uses & applications
Used primarily in construction as crushed stone or concrete aggregate, in the production of cement, and as a soil conditioner in agriculture.
Geological facts
This specimen contains white calcite veins where mineral-rich water filled fractures in the rock. Limestone makes up about 10% of the total volume of all sedimentary rocks on Earth.
Field identification & locations
Identify in the field by applying a drop of cold 5-10% hydrochloric acid; it will vigorously effervesce (fizz). Found commonly in bedded layers in areas that were once prehistoric seafloors.
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