State by State


  • Specimen Number


  • Description

    Irregular slab of strong reddish brown bedded rock with honeycomb structure and white matrix. Identified by survey staff at the University  of Iowa as a favosite, an extinct, colonial, tabular coral.

  • Classification

    Sedimentary. Limestone. Reef. Coral.

  • Location & Occurrence

    Marine reef created by extinct form of coral as part of a vast, shallow, epicontinental sea.

  • Geological Age

    Devonian.  448-251 Ma (Britannica).

  • Geoheritage

    Modern reefs are completely different, dominated by scleractinian corals.

  • Links

    Link to State Geological Map from USGS.  Link to Iowa Geological Survey.

  • Other

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Specimen stone for Iowa.
Closeup for Iowa Outline map of Iowa. Geo Map of Iowa