sedimentary
Limestone
Calcium Carbonate (CaCO3)
Hardness: 3 on Mohs scale; Color: typically light gray, tan, or white; Luster: earthy to dull; Crystal structure: trigonal (calcite-based); Cleavage: rhombohedral (in crystalline form); Specific gravity: 2.7.
- Hardness
- 3 on Mohs scale
- Color
- typically light gray, tan, or white
- Luster
- earthy to dull
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Physical properties
Hardness: 3 on Mohs scale; Color: typically light gray, tan, or white; Luster: earthy to dull; Crystal structure: trigonal (calcite-based); Cleavage: rhombohedral (in crystalline form); Specific gravity: 2.7.
Formation & geological history
Formed primarily in marine environments from the accumulation of shell, coral, algal, and fecal debris. It can also be formed by the chemical precipitation of calcium carbonate from lake or ocean water.
Uses & applications
Extensively used as a building material, aggregate for concrete, raw material for cement, soil conditioner in agriculture, and a pigment in various industrial products.
Geological facts
Limestone makes up about 10% of the total volume of all sedimentary rocks. It is the primary rock type in which most of the world's caves are formed through the process of chemical weathering.
Field identification & locations
Identify in the field by its softness (scratchable with a copper penny) and its reaction to dilute hydrochloric acid (it will fizz or effervesce). Commonly found in areas that were once under shallow, warm seas.
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