sedimentary
Limestone
Calcium Carbonate (CaCO3)
Hardness: 3 on Mohs scale. Color: White, cream, or light tan. Luster: Dull to earthy. Crystal Structure: Trigonal (as calcite). Cleavage: Perfect rhombohedral (in crystalline forms). Specific Gravity: 2.5-2.7.
- Hardness
- 3 on Mohs scale
- Color
- White, cream, or light tan
- Luster
- Dull to earthy
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Physical properties
Hardness: 3 on Mohs scale. Color: White, cream, or light tan. Luster: Dull to earthy. Crystal Structure: Trigonal (as calcite). Cleavage: Perfect rhombohedral (in crystalline forms). Specific Gravity: 2.5-2.7.
Formation & geological history
Formed primarily in shallow marine environments from the accumulation of shell, coral, algal, and fecal debris. It can also form chemically through the precipitation of calcium carbonate from lake or ocean water.
Uses & applications
Extensively used in construction as an aggregate for concrete and road base, in the manufacture of cement, as a flux in steel making, and as a soil conditioner in agriculture.
Geological facts
Limestone covers about 10% of the Earth's land surface and is the primary rock found in karst landscapes, where it dissolves to create massive cave systems. Most limestone contains significant quantities of fossils.
Field identification & locations
Identify in the field by its light color and its effervescence (fizzing) when a drop of diluted hydrochloric acid is applied. It is commonly found in quarry sites, road cuts, and regions with ancient sea beds.
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