sedimentary
Limestone (Weathered)
Sedimentary Carbonate Rock (CaCO3)
Hardness: 3 on Mohs scale; Color: Tan, buff, or light brown due to iron oxide staining; Luster: Dull/Earthy; Crystal structure: Microcrystalline calcite; Cleavage: None (rhombohedral in crystals); Specific gravity: 2.5-2.7
- Hardness
- 3 on Mohs scale
- Color
- Tan, buff, or light brown due to iron oxide staining
- Luster
- Dull/Earthy
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Physical properties
Hardness: 3 on Mohs scale; Color: Tan, buff, or light brown due to iron oxide staining; Luster: Dull/Earthy; Crystal structure: Microcrystalline calcite; Cleavage: None (rhombohedral in crystals); 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. Commonly found in Paleozoic to Cenozoic strata.
Uses & applications
Primarily used as a construction material, in cement production, as a soil conditioner in agriculture, and as a raw material for industrial chemicals.
Geological facts
Limestone makes up about 10% of the total volume of all sedimentary rocks on Earth. Most of the world's caves are formed in limestone because it is soluble in slightly acidic rainwater.
Field identification & locations
Identify in the field by its reaction to dilute hydrochloric acid (effervescence). Often found in outcrops where ancient seas once existed. For collectors, it may contain marine fossils.
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