sedimentary
Limestone
Sedimentary rock composed mainly of calcite (CaCO3)
Hardness: 3 on Mohs scale. Color: Usually white, gray, yellow, or tan. Luster: Earthy to dull. Crystal structure: Microcrystalline or fine-grained. Cleavage: None (fractures unevenly). Specific gravity: 2.7.
- Hardness
- 3 on Mohs scale
- Color
- Usually white, gray, yellow, or tan
- Luster
- Earthy to dull
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Physical properties
Hardness: 3 on Mohs scale. Color: Usually white, gray, yellow, or tan. Luster: Earthy to dull. Crystal structure: Microcrystalline or fine-grained. Cleavage: None (fractures unevenly). Specific gravity: 2.7.
Formation & geological history
Formed through the accumulation of organic debris such as shells, coral, and algal debris in shallow marine environments, or through the chemical precipitation of calcium carbonate from water.
Uses & applications
Extensively used in construction as building material, crushed stone for road base, an ingredient in concrete, and in agriculture for neutralizing soil acidity.
Geological facts
Limestone often contains fossils of ancient marine organisms since it forms from ocean sediment over millions of years. Famous structures like the Great Pyramids of Giza are built largely from 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.
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