sedimentary
Limestone with Calcite Crust
Sedimentary Calcium Carbonate (CaCO3)
Hardness: 3 (Mohs scale); Color: off-white to yellowish-tan; Luster: dull to earthy; Crystal structure: Trigonal (microcrystalline); Cleavage: rhombohedral in grains; Specific gravity: 2.7
- Hardness
- 3 (Mohs scale)
- Color
- off-white to yellowish-tan
- Luster
- dull to earthy
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Physical properties
Hardness: 3 (Mohs scale); Color: off-white to yellowish-tan; Luster: dull to earthy; Crystal structure: Trigonal (microcrystalline); Cleavage: rhombohedral in grains; Specific gravity: 2.7
Formation & geological history
Formed in shallow, warm marine environments through the accumulation of shell, coral, and algal debris, often with secondary mineralization like caliche or calcite crusting due to groundwater evaporation.
Uses & applications
Primarily used in construction, road aggregate, cement production, and as a flux in steel making. Also used as soil conditioner in agriculture.
Geological facts
Limestone makes up about 10% of the total volume of all sedimentary rocks. It is the primary material found in karst landscapes, resulting in the formation of caves.
Field identification & locations
Identified by its reaction (fizzing) with dilute hydrochloric acid. Commonly found in former seabed areas. For collectors, look for fossils or unusual crystalline formations on the surface.
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