sedimentary
Limestone Pebble
Sedimentary Calcium Carbonate (CaCO3)
Hardness: 3-4 (Mohs); Color: tan, grey, or off-white; Luster: dull to earthy; Structure: fine-grained/microcrystalline; Cleavage: none; Specific Gravity: 2.5-2.7
- Hardness
- 3-4 (Mohs)
- Color
- tan, grey, or off-white
- Luster
- dull to earthy
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Physical properties
Hardness: 3-4 (Mohs); Color: tan, grey, or off-white; Luster: dull to earthy; Structure: fine-grained/microcrystalline; Cleavage: none; Specific Gravity: 2.5-2.7
Formation & geological history
Formed in marine environments from the accumulation of shell, coral, algal, and fecal debris. It can also form through chemical precipitation from ocean water. Carboniferous to Cenozoic ages are common.
Uses & applications
Used extensively in construction (as aggregate), lime production, cement manufacturing, and soil acidity neutralization.
Geological facts
Limestone makes up about 10% of the total volume of all sedimentary rocks. It is the primary source of carbon for carbon dioxide in the atmosphere.
Field identification & locations
Identified in the field by its softness (can be scratched by steel) and its vigorous reaction (fizzing) when a drop of diluted hydrochloric acid is applied. Commonly found in riverbeds and coastal areas.
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