The thunderegg is a structure created in welded tuff or perlitic rocks.

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Gems and Minerals in Oregon

Thunderegg sites

Desolation Canyon Thundereggs
Desolation Canyon Thundereggs came from high in the Ochoco Mt's of Central Oregon north east of Prineville. All deposits are now in a strict area called Mill Creek Wilderness area and now closed to collecting.

McDermitt
This deposit is near the Oregon/Nevada Border. Near a town called McDermitt in Humbolt County. There are several Thunderegg deposits within this area. We know of 2 types - the Quinn River deposit and the Calico Deposit. We also have a red and yellow saginite from this area.

Steins Pillar Thundereggs
On your way south down Mill Creek Canyon is a geological formation known as Steins Pillar. Many years ago in the area around this formation there were some small thunderegg deposits.

Succor Creek
This deposit is in the far eastern part of Oregon almost on the border with Idaho. this was and is a very large deposit of Thundereggs. These thundereggs can get large as in excess of hundreds of pounds! But most are average sized up to grapefruit sized. Interesting specimens, but not much color. they are mostly a clear and white agate mix.

Maps and publications about Oregon’s Geology and its geologic treasures are available from the Nature of the Northwest Information Center,operated by the Oregon Department of Geology and Mineral Industries. Nature of the Northwest is open 9 am to 12:30 pm and 1 to 4 pm, Monday through Friday at: 800 NE Oregon Street #28, Suite 965,
Portland Oregon 97232,
phone (971) 673-2331, fax (971) 673-1562.
Web address: http://www.naturenw.org.