sedimentary
Limestone
Calcium Carbonate (CaCO3)
Hardness: 3 on Mohs scale; Color: Gray, tan, white, or buff; Luster: Dull to earthy; Texture: Fine-grained to clastic; Cleavage: None (fractures unevenly); Fizzes in contact with dilute hydrochloric acid.
- Hardness
- 3 on Mohs scale
- Color
- Gray, tan, white, or buff
- Luster
- Dull to earthy
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Physical properties
Hardness: 3 on Mohs scale; Color: Gray, tan, white, or buff; Luster: Dull to earthy; Texture: Fine-grained to clastic; Cleavage: None (fractures unevenly); Fizzes in contact with dilute hydrochloric acid.
Formation & geological history
Formed primarily in 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 road base and railroad ballast, in the production of cement, as a soil conditioner in agriculture, and for building stone.
Geological facts
Limestone makes up about 10% of the total volume of all sedimentary rocks. Most caves are formed in limestone due to its solubility in slightly acidic rainwater.
Field identification & locations
Identified in the field by its softness (can be scratched by a steel knife) and its strong reaction (effervescence) to weak acid. Found worldwide in ancient seabed deposits.
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