sedimentary
Limestone
Calcite (CaCO3)
Hardness: 3 on Mohs scale; Color: Grey, tan, or white; Luster: Dull to earthy; Crystal structure: Trigonal (microcrystalline in rock form); Cleavage: Perfect rhombohedral in calcite; Specific gravity: 2.7
- 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; Crystal structure: Trigonal (microcrystalline in rock form); Cleavage: Perfect rhombohedral in calcite; Specific gravity: 2.7
Formation & geological history
Formed primarily from the accumulation of shell, coral, algal, and fecal debris in warm, shallow marine waters. Can also form by the precipitation of calcium carbonate from lake or ocean water.
Uses & applications
Used extensively as a building material (cut stone), in the manufacture of cement, as a soil conditioner in agriculture, and as a raw material in the glass and chemical industries.
Geological facts
Limestone makes up about 10% of the total volume of all sedimentary rocks. It often contains abundant fossils that provide a record of ancient marine life.
Field identification & locations
Identify in the field by applying a drop of dilute hydrochloric acid; it will fizz (effervesce) vigorously. Often contains visible fossils or shell fragments. Found globally in areas that were once prehistoric sea beds.
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