Richardson's Rock Ranch

No. The ranch states that all digging is permanently closed. The rock shop remains open on seasonal hours and still sells freshly dug thundereggs from historic Priday beds, cut specimens, and lapidary goods. For dig-your-own thundereggs, use public sites such as White Fir Spring, Whistler Spring, or Succor Creek (souvenir limits inside the natural area).

Shop material is priced per pound and the ranch states that all prices are subject to change without notice. Shop orders carry a 5 pound minimum per rock type. Because published figures date quickly, call 541-475-2680 or 800-433-2680 for current shop pricing rather than relying on a guidebook number.

A spherulite that formed in rhyolitic ash and lava, with a rough brown exterior and an interior cavity later filled with agate, jasper or opal. The exterior gives no clue to the inside, which is the appeal: every egg is a sealed question until it is cut. Oregon made the thunderegg its state rock in 1965.

At 6683 NE Haycreek Road, Madras, Oregon, about 11 miles north of Madras off US Highway 97 in Jefferson County. Madras is roughly 45 minutes north of Bend and two and a half hours southeast of Portland. The ranch road is gravel but generally fine for a passenger car.

For a shop visit you need no digging tools. If you are continuing to public thunderegg beds the same trip, bring a pick or mattock, shovel, pry bar, gloves, safety glasses, a dust mask, and buckets — those sites are pick-and-shovel work.

The name comes from a Native American account recorded in central Oregon, in which the Thunder Spirits living on Mount Hood and Mount Jefferson threw the nodules at one another during storms. Oregon adopted the thunderegg as its state rock in 1965, and the name has been standard in the rock trade ever since.

With a diamond slab saw, cutting through the widest part of the nodule to expose the filled cavity, then polishing the face. Many rock shops will cut one for a small fee if you do not own a saw, and Richardson's shop sells cut faces so you can see what each bed produces before you dig.

Succor Creek State Natural Area in the Owyhee country of far eastern Oregon is the best known public option, where limited souvenir collecting by rock hounds is permitted. Several Bureau of Land Management areas in eastern and central Oregon also produce them, each with its own rules. Richardson's is the classic private fee dig.

Most commonly agate, in fortification bands that follow the cavity outline, or in a star pattern where the spherulite grew in points. Jasper and opal fills also occur. Colour and pattern are characteristic of the bed the egg came from, which is why collectors at a ranch choose a bed rather than just a site.

Dense enough to catch people out. A solid silica-filled nodule the size of a grapefruit is surprisingly heavy, and a bucket fills to its weight limit long before it fills to the brim. Bring several buckets, load them partway, and plan the carry back to the vehicle before you dig.

Richardson's no longer offers a fee dig. Collectors who want a managed first dig should look for currently open private mines elsewhere, or learn on public Forest Service beds and Succor Creek. The ranch shop is still valuable for seeing cut faces before you dig elsewhere.

The advice that gets repeated is to look for the shape and the rind rather than for anything that resembles a gemstone. Thundereggs come out roughly spherical to knobbly, with a distinctive rough exterior that differs in texture from the surrounding ash, and they often have a faint seam. Experienced diggers also mention weight: a thunderegg feels heavier than a similar-sized piece of country rock. Beyond that, nobody can call an interior from the outside, which is the entire appeal.