State by State


  • Specimen Number


  • Description

    Half-boulder of unknown rock, silicified limestone, which slowly fizzes in dilute hydrochloric acid. Close up shows granular texture with irregular horizons, possibly cherty beds or silica replacement horizons.

  • Classification

    Sedimentary. Limestone.  Silicified.

  • Location & Occurrence

    Formed on ancient sea floor.

  • Geological Age

    Likely Early to Mid Paleozoic.

  • Geoheritage

    Part of the flat-lying rocks of the platform of the central United States.

  • Links

    Link to State Geological Map from USGS.  Link to Geological Survey of Illinois.

  • Other

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Specimen stone for Illinois.
Closeup of Illinois Outline of Illinois Geo Map of Illinois