sedimentary
Limestone
Calcium Carbonate (CaCO3)
Hardness: 3 on Mohs scale; Color: typically gray, white, or tan; Luster: dull to earthy; Crystal structure: Trigonal (as calcite); Cleavage: Perfect rhombohedral in calcite crystals; Specific gravity: 2.71
- Hardness
- 3 on Mohs scale
- Color
- typically gray, white, or tan
- Luster
- dull to earthy
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Physical properties
Hardness: 3 on Mohs scale; Color: typically gray, white, or tan; Luster: dull to earthy; Crystal structure: Trigonal (as calcite); Cleavage: Perfect rhombohedral in calcite crystals; Specific gravity: 2.71
Formation & geological history
Formed primarily from the accumulation of shell, coral, algal, and fecal debris in marine environments through chemical precipitation or biological activity. It can date back to any geological age from the Precambrian to Holocene.
Uses & applications
Extensively used in construction (aggregate, cement manufacture), agriculture (soil conditioner), industrial chemistry (flue gas desulfurization), and as a building stone.
Geological facts
Limestone covers about 10% of the Earth's total land surface. It is the primary rock type found in 'Karst' topography, where it dissolves to form spectacular cave systems and sinkholes.
Field identification & locations
Can be identified in the field by its 'fizzing' reaction when exposed to a drop of dilute hydrochloric acid. It is found globally in areas that were once ancient sea beds, such as the Midwestern US, the UK, and Southern Europe.
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