sedimentary
Limestone
Sedimentary Limestone (Calcium Carbonate, CaCO3)
Mohs hardness: 3; Color: Gray, tan, or yellowish-white; Luster: Dull to earthy; Crystal structure: Trigonal (microcrystalline); Specific gravity: 2.5-2.7
- Hardness
- 3
- Color
- Gray, tan, or yellowish-white
- Luster
- Dull to earthy
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Physical properties
Mohs hardness: 3; Color: Gray, tan, or yellowish-white; Luster: Dull to earthy; Crystal structure: Trigonal (microcrystalline); Specific gravity: 2.5-2.7
Formation & geological history
Formed in marine environments from the accumulation of shell, coral, algal, and fecal debris. It can also form through chemical precipitation from ocean or lake water.
Uses & applications
Extensively used in construction as an aggregate, cement production, and as a flux in steel making. Also used as a soil conditioner in agriculture.
Geological facts
Limestone makes up about 10% of the total volume of all sedimentary rocks. It is the primary rock type found in karst landscapes, which feature caves and sinkholes.
Field identification & locations
Identified in the field by its softness (can be scratched by a steel knife) and its reaction to dilute hydrochloric acid (effervescence). Commonly found in areas that were once prehistoric seafloors.
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