sedimentary
Limestone
Calcium Carbonate (CaCO3)
Hardness: 3 on Mohs scale; Color: tan, grey, or white; Luster: dull; Crystal Structure: trigonal (when crystalline); Cleavage: rhombohedral; Specific Gravity: 2.5-2.7
- Hardness
- 3 on Mohs scale
- Color
- tan, grey, or white
- Luster
- dull
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Physical properties
Hardness: 3 on Mohs scale; Color: tan, grey, or white; Luster: dull; Crystal Structure: trigonal (when crystalline); Cleavage: rhombohedral; 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 be formed by the chemical precipitation of calcium carbonate from lake or ocean water.
Uses & applications
Used primarily in construction for building stone and road base, in the production of cement, as a decorative stone, and as a soil conditioner in agriculture.
Geological facts
Limestone makes up about 10% of the total volume of all sedimentary rocks. Most caves, such as Mammoth Cave in Kentucky, are formed by the dissolution of limestone by acidic groundwater.
Field identification & locations
Identify in the field by its reaction to dilute hydrochloric acid (it will fizz) and its tendency to contain marine fossils. Common in areas that were once ancient seabeds.
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