sedimentary
Fossiliferous Limestone
Biogenic Limestone (Calcium Carbonate, CaCO3)
Hardness: 3-4 (Mohs); Color: Gray, tan, or buff; Luster: Dull/Earthy; Crystal Structure: Microcrystalline with visible fossil inclusions; Cleavage: None/Irregular; Specific Gravity: 2.3 - 2.7.
- Hardness
- 3-4 (Mohs)
- Color
- Gray, tan, or buff
- Luster
- Dull/Earthy
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Physical properties
Hardness: 3-4 (Mohs); Color: Gray, tan, or buff; Luster: Dull/Earthy; Crystal Structure: Microcrystalline with visible fossil inclusions; Cleavage: None/Irregular; Specific Gravity: 2.3 - 2.7.
Formation & geological history
Formed in shallow, warm marine environments where biological debris like shells and skeletal remains accumulate. Over millions of years, compaction and cementation by calcium carbonate create the rock.
Uses & applications
Used in construction as a building material, road base, or cement ingredient. In agriculture, it is crushed for soil treatment. Collector value depends on fossil preservation.
Geological facts
Limestone covers about 10% of the Earth's total land surface. It often contains fossils of crinoids, brachiopods, or corals, providing a window into prehistoric marine life.
Field identification & locations
Identify by applying a drop of vinegar or diluted hydrochloric acid; it will fizz (effervesce). Look for visible shell fragments or organic patterns on weathered surfaces. Commonly found in areas that were once ancient inland seas.
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