sedimentary
Limestone Pebble
Limestone (Calcium Carbonate, CaCO3)
Hardness: 3-4 (Mohs scale); Color: Gray to tan; Luster: Dull/Earthy; Crystal Structure: Trigonal (microcrystalline); Cleavage: None/Irregular
- Hardness
- 3-4 (Mohs scale)
- Color
- Gray to tan
- Luster
- Dull/Earthy
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Physical properties
Hardness: 3-4 (Mohs scale); Color: Gray to tan; Luster: Dull/Earthy; Crystal Structure: Trigonal (microcrystalline); Cleavage: None/Irregular
Formation & geological history
Formed primarily from the accumulation of shell, coral, algal, and fecal debris in marine environments. It can also form through chemical precipitation from lake or ocean water.
Uses & applications
Used extensively in construction as road base, railroad ballast, and an ingredient in cement. Finer grades are used in agriculture and as industrial filler.
Geological facts
Limestone makes up about 10% of the total volume of all sedimentary rocks on Earth. It is the primary source of 'karst' topography, which includes caves and sinkholes.
Field identification & locations
Can be identified in the field by its tendency to fizz when a small amount of dilute acid (like vinegar) is applied. Often found in areas that were once prehistoric seabeds.
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