sedimentary
Fossiliferous Limestone
Biogenic Sedimentary Rock (Calcium Carbonate, CaCO3)
Hardness: 3 on the Mohs scale; Color: Gray, tan, or brown with lighter fossil impressions; Luster: Dull to earthy; Crystal structure: Microcrystalline calcite; Cleavage: Perfect rhombohedral in calcite crystals; Specific gravity: 2.7 - 2.9
- Hardness
- 3 on the Mohs scale
- Color
- Gray, tan, or brown with lighter fossil impressions
- Luster
- Dull to earthy
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Physical properties
Hardness: 3 on the Mohs scale; Color: Gray, tan, or brown with lighter fossil impressions; Luster: Dull to earthy; Crystal structure: Microcrystalline calcite; Cleavage: Perfect rhombohedral in calcite crystals; Specific gravity: 2.7 - 2.9
Formation & geological history
Formed from the accumulation and compaction of organic debris such as shells, coral, algal, and other skeletal fragments in shallow marine environments, predominantly during the Paleozoic, Mesozoic, and Cenozoic eras.
Uses & applications
Used primarily in the construction industry as crushed stone for road base, railway ballast, aggregate in concrete, as well as in the production of cement and agricultural lime.
Geological facts
Limestone often weathers to form dramatic karst topography, including caves, sinkholes, and underground rivers. The small circular or oval patterns visible on this specific fragment are typical cross-sections of fossilized crinoid stem ossicles or brachiopods.
Field identification & locations
Can be easily identified by its reaction to dilute hydrochloric acid, which causes it to effervesce (fizz) due to the presence of calcium carbonate. Commonly found worldwide in regions with ancient marine sedimentary basins.
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