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The Formation of Thundereggs (Lithophysae)

By Robert Paul Colburn


Book’s Key Features

·         Complete model of thunderegg formation based on cristobalite crystallization.

·         The formation of thundereggs related to obsidian and perlite occurrences, especially lava domes.

·         An extensive photo collection of geodes, thundereggs, and their inclusions.

·         An extensive list of thunderegg sites in the west.

·         A detailed discussion of the formation of thundereggs from flow-banded rhyolitic lava.

·         An extensive review of obsidian flow formation with a new model presented.

·         A detailed account of how biconoid thunderegg cores relate to thunderegg genesis.

·         Unusual agate structures such as flow-stretched and tube lithophysae are documented.

·         A complete Lexicon of geode and thunderegg structural terms is included.

·         Substantial advice and diagrams are provided how to properly cut thundereggs.


“I owe you so much - discussions about thundereggs, thunderegg images…”

Dr. Peter Woerner, author “Geodes and Thundereggs in Rhyolite”



 “You are the Thunderegg Guru!” 

 “I continue to be amazed at your ability to synthesize scientific data.”

Doug Moore


“Your insights on agates…exceed mine.  So I just mean to say thank you.”

John Marshall, author “The ‘Other’ Lake Superior Agates”



“I have been a big fan of yours for many, many years.”

Brad Cross, co-author “Geodes: Nature’s Treasures” with June Zeitner



“Perhaps you now have my new publications, which would be impossible without your help.  Thank you so much!”  Peter Wagenblast



    "I'm always glad to publicize your work and to speak well of it."

John Stockwell


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