sedimentary
Limestone
Calcium Carbonate (CaCO3)
Hardness: 3 on Mohs scale; Color: Grey, tan, or white; Luster: Dull to earthy; Texture: Fine to medium grained; reacts with dilute hydrochloric acid.
- 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; Texture: Fine to medium grained; reacts with dilute hydrochloric acid.
Formation & geological history
Formed primarily from the accumulation of shell, coral, algal, and fecal debris in marine environments. It can also form through chemical precipitation from ocean water or groundwater.
Uses & applications
Extensively used in construction, road base, cement manufacturing, agriculture (as soil conditioner), and as a flux in steel making.
Geological facts
Limestone covers about 10% of the Earth's land surface. Most caves are formed in limestone because it dissolves relatively easily in slightly acidic water.
Field identification & locations
Identifiable by its reaction to acid (fizzing) and its relative softness compared to quartz. Commonly found in areas with a history of ancient shallow seas.
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