• Specimen Number

  11

• 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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