sedimentary
Limestone
Calcium Carbonate (CaCO3)
Hardness: 3 on Mohs scale; Color: Light gray, tan, yellowish, or white; Luster: Earthy to sub-vitreous; Crystal structure: Trigonal (as calcite); Cleavage: Perfect rhombohedral; Specific gravity: 2.71
- Hardness
- 3 on Mohs scale
- Color
- Light gray, tan, yellowish, or white
- Luster
- Earthy to sub-vitreous
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Physical properties
Hardness: 3 on Mohs scale; Color: Light gray, tan, yellowish, or white; Luster: Earthy to sub-vitreous; Crystal structure: Trigonal (as calcite); Cleavage: Perfect rhombohedral; Specific gravity: 2.71
Formation & geological history
Formed through the accumulation of skeletal fragments of marine organisms such as coral, algal, and foraminifera, as well as the chemical precipitation of calcium carbonate from water.
Uses & applications
Widely used in construction as building stone, aggregate for roads, production of quicklime, cement manufacture, and agricultural soil treatment.
Geological facts
Limestone often contains fossils of ancient marine life and can dissolve in mildly acidic water, creating spectacular cave systems and karst topography.
Field identification & locations
Easily identified by its reaction to dilute hydrochloric acid, which causes it to effervesce (fizz) due to the release of carbon dioxide gas. Commonly found in sedimentary basins worldwide.
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