sedimentary
Fossilized Coral
Scleractinian Anthozoa (Fossilized Calcium Carbonate, CaCO3)
Hardness: 3-4 (Mohs scale); Color: White to off-white/beige; Luster: Dull to earthy; Structure: Visible skeletal corallites with septal patterns; Specific Gravity: 2.5–2.7
- Hardness
- 3-4 (Mohs scale)
- Color
- White to off-white/beige
- Luster
- Dull to earthy
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Physical properties
Hardness: 3-4 (Mohs scale); Color: White to off-white/beige; Luster: Dull to earthy; Structure: Visible skeletal corallites with septal patterns; Specific Gravity: 2.5–2.7
Formation & geological history
Formed through the fossilization of ancient marine coral reefs. Over millions of years (often from the Silurian to the Neogene periods), the organic matter is replaced by minerals or the carbonate skeleton is lithified into limestone in shallow marine environments.
Uses & applications
Used primarily in landscaping (rock gardens), construction as an aggregate, aquarium decoration, and as display specimens for collectors. Highly silica-replaced versions (Agatized Coral) are used in jewelry.
Geological facts
Fossilized coral is a 'stone' that was once a living creature. Ancient coral reefs can be found in land-locked locations like Michigan or Florida, indicating where ancient oceans once covered the continents.
Field identification & locations
Identify by looking for radial, star-shaped, or hive-like patterns (corallites) on the surface. Commonly found in limestone quarries, coastal areas, and ancient sea beds. It reacts with acid (effervescence) due to its calcium carbonate content.
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