sedimentary
Fossil Coral
Cnidaria fossil (often Calcium Carbonate / CaCO3)
Hardness: 3-4 (Mohs scale), Color: Cream/white/gray, Luster: Dull/earthy to waxy, Crystal Structure: Orthorhombic/Hexagonal (originated as aragonite or calcite), Cleavage: None, Specific Gravity: 2.6-2.8
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Physical properties
Hardness: 3-4 (Mohs scale), Color: Cream/white/gray, Luster: Dull/earthy to waxy, Crystal Structure: Orthorhombic/Hexagonal (originated as aragonite or calcite), Cleavage: None, Specific Gravity: 2.6-2.8
Formation & geological history
Formed from the skeletons of marine polyps. Over millions of years, biological remains are buried under sediment and mineralized, typically dating from the Ordivician to the Holocene periods.
Uses & applications
Used in landscaping, jewelry (beads/cabochons), aquarium decoration, and as geological teaching specimens.
Geological facts
Many fossil corals are found in the middle of continents, such as Petoskey stones in Michigan, proving that those areas were once covered by shallow tropical seas.
Field identification & locations
Identify by looking for repeating poly-pitting or 'floral' patterns on the surface. Find them on ancient shorelines or in limestone quarries. Collectors look for high definition in the fossilized structure.
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