Where is Fossil Coral found?
Fossilized Rugose or Tabulate Coral (Chalcedony/Agate)
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Open the appFossil Coral occurs in specific geological environments. Knowing where to look, and in what kind of rock, is the difference between going home empty-handed and finding a great specimen.
Where to find Fossil Coral
Florida, USA
Known for 'Tampa Bay Coral' or 'Florida Agatized Coral,' primarily from the Miocene-Pliocene Hawthorn Group. These often show excellent preservation of coral structures, particularly from scleractinian corals.
Michigan, USA
Famous for 'Petoskey Stone,' which is specifically fossilized Hexagonaria percarinata, a rugose coral from the Devonian Traverse Group. It is the state stone of Michigan.
Indonesia (especially Sumatra)
Produces a wide variety of fossil corals, often with vibrant colors and intricate patterns, from various geological periods.
Morocco
Known for Devonian rugose and tabulate corals, often found in limestone formations, some of which are silicified.
Utah, USA
Various locations yield silicified corals, often associated with other fossiliferous deposits.
Australia
Certain regions, particularly in Queensland, have occurrences of silicified corals.
Collecting tips
- Look in Sedimentary Deposits. Focus on areas known for ancient marine sedimentary rocks, especially limestones, shales, and gravel beds that have eroded from such formations. Riverbeds and beach gravels can also yield specimens.
- Identify Coral Structures. Look for characteristic coral patterns: hexagonal cells (like Petoskey Stone), radial lines, or honeycomb structures. Even if the external shape is irregular, the internal pattern is key.
- Check for Hardness. Silicified coral will be significantly harder than un-silicified calcium carbonate coral. It will scratch glass and will not fizz with dilute hydrochloric acid (unless there are residual carbonate inclusions).
- Observe Luster and Fracture. Polished specimens will have a waxy to vitreous luster. Freshly broken surfaces will exhibit a conchoidal fracture, typical of chalcedony/agate.
- Research Local Geology. Consult geological maps and reports for areas known to contain fossiliferous marine strata, particularly those with evidence of silicification.
Quick Check
- Color:
- Variable (white, gray, brown, black, yellow, pink, red, blue), often patterned.
- Luster:
- Waxy to vitreous (polished), dull to earthy (unpolished).
- Streak:
- White.
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