Some eggs contain brecciated rock fragments, while others show faulting, offset, and healing. One of the most unusual Thunderegg variants is up to 3 feet long and 2 to 3 inches in diameter and looks much like a fat gray worm. In some areas, it is common to find the characteristic chalcedony core weathered out of its shell. If a complete egg is sawed in the right orientation, one or more conduits through which filling materials flowed may be found. The beauty and complexities of many of the cut and polished eggs explain why Oregon rockhounds have long been fascinated by Thundereggs.
Some localities occur in beautiful forested hill country, others in dry, desertlike terrain.
Proper equipment, including shovel, pick, and bar, makes the job much easier. Eggs often may be purchased and equipment rented at the site office. Conditions change, so collectors should contact sites for current fee status and appropriate authorities for permission to dig. The sites are grouped into four major collecting areas. Addresses and phone numbers are those you should contact for information.