sedimentary
Limestone
Sedimentary rock composed primarily of calcium carbonate (CaCO3)
Hardness: 3 on Mohs scale; Color: White, gray, tan, yellow, or brown; Luster: Earthy to vitreous; Structure: Microcrystalline to granular; Cleavage: Poor, but exhibits distinct rhombohedral parting in calcite crystals; Specific Gravity: 2.7 to 2.9
- Hardness
- 3 on Mohs scale
- Color
- White, gray, tan, yellow, or brown
- Luster
- Earthy to vitreous
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Physical properties
Hardness: 3 on Mohs scale; Color: White, gray, tan, yellow, or brown; Luster: Earthy to vitreous; Structure: Microcrystalline to granular; Cleavage: Poor, but exhibits distinct rhombohedral parting in calcite crystals; Specific Gravity: 2.7 to 2.9
Formation & geological history
Formed by the accumulation of skeletal fragments of marine organisms such as coral, algae, and foraminifera, or through the chemical precipitation of calcium carbonate from water in marine and freshwater environments over millions of years.
Uses & applications
Widely used in construction as building stone and aggregate in concrete, as a raw material for manufacturing cement, in agriculture to neutralize acidic soils, and in the production of lime and glass.
Geological facts
Limestone often contains fossils of ancient sea life since it forms in shallow marine waters. Famous structures like the Great Pyramid of Giza and parts of the Empire State Building utilize limestone.
Field identification & locations
Can be easily identified in the field by applying a drop of dilute hydrochloric acid, which will cause it to fizz and effervesce due to the release of carbon dioxide. Commonly found worldwide in sedimentary basins and mountain ranges.
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