sedimentary
Limestone
Calcium carbonate ( преимущественно CaCO3)
Hardness: 3 on Mohs scale; Color: Gray, tan, white, or light brownish; Luster: Dull to earthy; Crystal structure: Trigonal/Hexagonal (usually microcrystalline); Cleavage: Perfect rhombohedral in calcite crystals, but rarely visible in bulk samples; Specific gravity: 2.5 - 2.8.
- Hardness
- 3 on Mohs scale
- Color
- Gray, tan, white, or light brownish
- Luster
- Dull to earthy
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Physical properties
Hardness: 3 on Mohs scale; Color: Gray, tan, white, or light brownish; Luster: Dull to earthy; Crystal structure: Trigonal/Hexagonal (usually microcrystalline); Cleavage: Perfect rhombohedral in calcite crystals, but rarely visible in bulk samples; Specific gravity: 2.5 - 2.8.
Formation & geological history
Formed primarily in shallow marine environments from the accumulation of shell, coral, algal, and fecal debris. It can also form through the chemical precipitation of calcium carbonate from lake or ocean water. Most deposits span from the Paleozoic to the Mesozoic era.
Uses & applications
Extensively used in construction (as aggregate and building stone), cement production, as a soil conditioner in agriculture, and for the manufacturing of lime and glass. Specific dense varieties are used as dimension stone for facades.
Geological facts
Limestone covers about 10% of the Earth's land surface and is the primary rock type in karst landscapes, which feature caves and sinkholes. Some of the most famous structures in history, including the Great Pyramid of Giza and many European cathedrals, are built from limestone.
Field identification & locations
Identify in the field by its light gray to tan color and its strong effervescence (fizzing) when a drop of diluted hydrochloric acid or strong vinegar is applied. It is commonly found in regions that were once prehistoric seafloors, such as the Midwestern United States, the UK, and Central Europe.
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