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

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Gems and Minerals in Oregon

Thundereggs
The thunderegg is Oregon’s state rock.

Oregon’s state rock can be collected at fee and free sites in central and southeastern Oregon. Unimpressive on the outside, these spherical rocks contain colorful silicic material and, when sliced and polished, make beautiful collector’s items.

For information on places to collect in central Oregon, contact

Madras Chamber of Commerce, 197 SE 5th St., Madras OR 97741, phone 541-475-2350;

Prineville Chamber of Commerce, 390 North Fairview, Prineville, OR 97754, phone 541-447-6304,

In Southeastern Oregon contact the Bureau of Land Management (BLM), 100 Oregon Street, Vale OR 97918, phone (541) 473-3144,

To find out more about Thunderegg Days (held for five days around the first of June), in Nyssa, contact the Nyssa Chamber of Commerce at   (541) 372-3091.

More on Thunderegg sites in Oregon

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.