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Learn More About Oregon's Geology
Gems and Minerals in Oregon

Please be aware it is illegal to alter, damage, or destroy an archeological site on any lands, per Oregon Revised Statute 358.920.
The thunderegg is Oregon’s state rock.
The thunderegg is a structure created in welded tuff or perlitic rocks.

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, 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,
  • Richardson’s Recreational Ranch, Gateway Route, Box 440, Madras, OR 97741, phone 541-475-2680 or 541-475-2839. This is a commercial site.
  • Lucky Strike Mine, PO Box 128, Mitchell, OR 97750 Phone: 541-462-3073. This is a commercial site.

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

Find out more about the Thunderegg Days and Festival in Nyssa.

Thundereggs from this spot contain both Agate and Jasper filled cores. The cores also have the shape of a diamond (biconic). Head east from Prineville on US 26 to MP 41. Turn left on 3350 and head up the road for about 5 1/2 miles... don´t turn on any of the spur roads. Once you reach a sign saying Chamber of Commerce Claim you are at the jasper core locality. For agate-filled thundereggs, turn right on the road just before you reach the jasper deposit.