sedimentary
Fossiliferous Limestone
Biogenic Calcium Carbonate (CaCO3)
Hardness: 3 on Mohs scale; Color: Gray, tan, or white; Luster: Dull to earthy; Structure: Clastic or crystalline with visible fossil fragments; Cleavage: None (rhombohedral in calcite crystals within); Specific Gravity: 2.3-2.7
- Hardness
- 3 on Mohs scale
- Color
- Gray, tan, or white
- Luster
- Dull to earthy
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Physical properties
Hardness: 3 on Mohs scale; Color: Gray, tan, or white; Luster: Dull to earthy; Structure: Clastic or crystalline with visible fossil fragments; Cleavage: None (rhombohedral in calcite crystals within); Specific Gravity: 2.3-2.7
Formation & geological history
Formed in marine environments from the accumulation of shell, coral, algal, and fecal debris. Over millions of years, these sediments are lithified through compaction and cementation. Often dates from the Paleozoic to Cenozoic eras.
Uses & applications
Used widely in construction as building stone, road base, and as a primary ingredient in cement. It is also used in agriculture to neutralize soil acidity and as a flux in steel making.
Geological facts
Limestone covers about 10% of the Earth's land surface. It is the primary rock type found in karst landscapes, resulting in spectacular caves and sinkholes.
Field identification & locations
Identify in the field by applying a drop of dilute hydrochloric acid; it will effervesce (fizz). Look for visible imprints or fragments of ancient marine life. Commonly found in areas that were once prehistoric seabeds.
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