sedimentary
Limestone
Calcium Carbonate (CaCO3)
Hardness: 3 on Mohs scale; Color: Gray, tan, or white; Luster: Dull to earthy; Structure: Fine-grained with potential fossil inclusions; Specific gravity: 2.3-2.7.
- Hardness
- 3 on Mohs scale
- Color
- Gray, tan, or white
- Luster
- Dull to earthy
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Physical properties
Hardness: 3 on Mohs scale; Color: Gray, tan, or white; Luster: Dull to earthy; Structure: Fine-grained with potential fossil inclusions; Specific gravity: 2.3-2.7.
Formation & geological history
Forms in marine environments by the accumulation of shell, coral, algal, and fecal debris. It can also form through chemical precipitation from lake or ocean water.
Uses & applications
Primarily used in construction as aggregate, in cement production, for soil conditioning in agriculture, and as a chemical feedstock.
Geological facts
Limestone covers about 10% of the Earth's total land surface. Most caves are formed in limestone because it is easily dissolved by acidic groundwater.
Field identification & locations
Identify by its reaction to cold dilute hydrochloric acid (it will fizz). Commonly found in riverbeds, quarries, and coastal cliffs. Collectors look for fossilized remains within the matrix.
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