sedimentary
Limestone
Sedimentary rock composed primarily of Calcite (CaCO3)
Hardness: 3 (Mohs scale); Color: Gray, tan, or white; Luster: Dull/Earthy; Structure: Fine-grained/Microcrystalline; Cleavage: None (has conchoidal or irregular fracture); Specific Gravity: 2.5-2.7
- Hardness
- 3 (Mohs scale)
- Color
- Gray, tan, or white
- Luster
- Dull/Earthy
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Physical properties
Hardness: 3 (Mohs scale); Color: Gray, tan, or white; Luster: Dull/Earthy; Structure: Fine-grained/Microcrystalline; Cleavage: None (has conchoidal or irregular fracture); Specific Gravity: 2.5-2.7
Formation & geological history
Biological sedimentary formation, often from the accumulation of shell, coral, algal, and fecal debris in warm, shallow marine waters. Can also form through chemical precipitation from lake or ocean water.
Uses & applications
Extensively used in construction as aggregate, for making cement/mortar, as a soil conditioner in agriculture, and for the production of lime.
Geological facts
Limestone makes up about 10% of the total volume of all sedimentary rocks. It is the primary host for karst landscapes including caves and sinkholes.
Field identification & locations
Identifiable in the field by its softness (can be scratched by a steel nail) and its effervescence (bubbling) when a drop of dilute hydrochloric acid or vinegar is applied. Found globally in ancient seabed deposits.
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