sedimentary
Limestone
Calcium carbonate (CaCO3)
Hardness: 3-4 (Mohs), Color: Light gray to white, Luster: Earthy to dull, Crystal structure: Microcrystalline or fine-grained texture, Cleavage: None visible, Specific gravity: 2.5-2.7
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Physical properties
Hardness: 3-4 (Mohs), Color: Light gray to white, Luster: Earthy to dull, Crystal structure: Microcrystalline or fine-grained texture, Cleavage: None visible, Specific gravity: 2.5-2.7
Formation & geological history
Formed from marine deposits of calcium carbonate, often containing microscopic fossil fragments. Often dates back hundreds of millions of years to ancient shallow seas.
Uses & applications
Used widely in construction (aggregate, cement), agriculture (soil conditioning), and industry.
Geological facts
Limestone covers about 10% of the Earth's continental surface and is essential for the carbon cycle.
Field identification & locations
Fizzes vigorously when a drop of dilute hydrochloric acid is applied. Can be found globally in sedimentary basins.
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