Thunderegg Information

The official Oregon State Rock

The Thunderegg became the Oregon state rock on March 29, 1965. On that day Senate Joint Resolution 18 was passed, whereupon the Thunderegg joined the other nature symbols of Oregon.
Senate Joint Resolution 18 was passed in the Senate, 23 to 2, and in the House, 48 to 5. Because it was a Joint Resolution, it did not have to be signed by the Governor, and became the "law of the land" in effect, by the signatures of President Boivin and Speaker Montgomery on the date of March 29, 1965.

How Thundereggs Form

Thundereggs are agate-filled nodules found in various parts of the Western United States. They range in size from about a 1/4 to over 5 foot in diameter; generally, however, the size of oranges. All are similar on the exterior, but no two are alike in the interior. In spite of their superior general quality, only one in an average of 20 cut, make outstanding specimens. These show vivid scenes of land and sea fantasies which, besides the bright hues, reveal the appearence of depth and dimensions of distance. Cut and polished Thundereggs are beautifull to behold. They are indeed, one of the marvels of Nature and are sought after and highly prized the world over.
The unique, agate-filled mud balls are found in layers of ryholite lava flows which spread over the land an estimted 60 million years ago. This was long before man appeared on Earth and thousands of centries before the Cascade Mountain Range were formed and pushed upward, due to tremendous stresses beneath the surface of the globe on which we dwell. Geologists reason that Thundereggs were formed in gas pockets, serving as molds, left in the lava flows of the Eocene Geological Age. They say further, that, over long periods of time the gas pockets were filled by water actions, percolating through the porous rock formations. Water (hot/cold) oozing into the cavities, carrying rich quantities of silica (quartz) in solution, lined, and in many cases, filled the cavity molds, first with the darker matrix material, then, the inner core of agate or chalcedony. The beautifull colors were derived from nearby minerals present. They also form with agate, jasper, common opal, precious opal, fire opal, ect....
Information used from free paper provided from Richardsons Ranch Thunderegg Beds

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