There had been a few finds of thundereggs in the rhyolite outcrops near Grand Marias, Minnesota and even few agate cores were found along the beaches.  A number of thundereggs was extracted from underwater of Lake Superior by scuba diving. Many came with quartz cores usually lined with thin red to pink agate bands. Some tumbled thundereggs have been along the beaches of Michigan to the east of Grand Marias also.
    It must be cautioned that there had been claims of finding foreign thundereggs in the gravel pits which may be dumped by old-time collectors who brought them from the western states. Baker Egg thundereggs, Mexican Coconuts, common Petrified wood and Oregon thundereggs are the examples that had been dumped in the landfills and old gravel pits.

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