sedimentary
Limestone
Calcium Carbonate (CaCO3)
Hardness: 3 on Mohs scale; Color: Grey, tan, or white; Luster: Dull to earthy; Crystal Structure: Trigonal (microcrystalline); Cleavage: None (rhombohedral in calcite crystals); Specific Gravity: 2.5-2.7
- Hardness
- 3 on Mohs scale
- Color
- Grey, tan, or white
- Luster
- Dull to earthy
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Physical properties
Hardness: 3 on Mohs scale; Color: Grey, tan, or white; Luster: Dull to earthy; Crystal Structure: Trigonal (microcrystalline); Cleavage: None (rhombohedral in calcite crystals); Specific Gravity: 2.5-2.7
Formation & geological history
Formed primarily from the accumulation of shell, coral, algal, and fecal debris in warm, shallow marine waters. Can also form through chemical precipitation from ocean or lake water.
Uses & applications
Extensively used in construction (crushed stone, concrete), architecture, lime production, agriculture (soil sweetener), and as a flux in steel manufacturing.
Geological facts
Limestone accounts for about 10% of the total volume of all sedimentary rocks. It often contains abundant fossils that provide clues about ancient marine environments.
Field identification & locations
Can be identified in the field by its effervescence (fizzing) when a drop of dilute hydrochloric acid is applied. Commonly found in massive beds or layers in areas that were once prehistoric seafloors.
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