PRINEVILLE — Every year they come from all over the world, armed with maps, shovels and a shared goal: finding the perfect rock.

With a diverse, colorful landscape created by volcanic eruptions millions of years ago, Central Oregon is a well-known destination for rockhounds of all ages. And no matter where they’re heading or what they’re searching for — thunder eggs or agates, jasper or obsidian — most of the geologic treasure hunters pass through Crook County, where rockhounds account for a majority of visitors who stop at the Prineville-Crook County Chamber of Commerce, according to its executive director.

Rocks are big business in Prineville, especially at Judy Elkins’ small but well-stocked rock and gem store, Elkins Gem Stones, on South Main Street. For more than three decades, Elkins has been greeting people from as far away as France, Japan and New Zealand, rockhounds who travel halfway around the world for their chance to dig in the dirt of the Ochoco National Forest or any number of other rockhounding hot spots in the area.

She gives each visitor two photocopied maps and takes out a red pen, circling the best spots — Whistler and White Fir Springs for thunder eggs, Glass Butte for obsidian — and sends them on their way.

“Sometimes there are 10, 15 a day at least,” Elkins said. “Sometimes you have days when no one shows up, and then the next day it’s ‘Take a number and wait.’ I swear I’m going to get a video- tape of me giving directions on this map — by the end of the summer I’ve said this so many times that I can’t even say it straight anymore.”

Unique landscape

Local restaurants, shops and hotels can thank volcanic activity that occurred between 40 million and 50 million years ago for the boost they get from modern rockhounds traveling through the High Desert.

After a band of volcanoes stretching across the area erupted, silica-rich groundwater filled the cracks of rocks with quartz, agate and jasper, said Ochoco National Forest geologist Carrie Gordon. More recent volcanic activity — a mere 4.9 million years ago — at the Glass Buttes in Lake County, just below Deschutes County’s southern border, produced flows of molten volcanic glass and covered the area with deposits of obsidian.

And then there’s the thunder egg, the ball-shaped state rock of Oregon that’s one of the most popular finds for rockhounds. Often filled with crystals, agate or jasper, thunder eggs are the result of pockets of gas frozen in place as molten rocks cooled after a long-ago volcanic eruption, Gordon said.

“The (rock) material itself is one of the best parts about living here, because of the geologic history of the area,” she said.

In Crook County and throughout Central Oregon, the places to hunt for rocks are almost as plentiful as the rocks themselves. Some sites, including private lands, protected wilderness study areas and wilderness areas are off-limits, but the U.S. Forest Service and the Bureau of Land Management allow rockhounds to try their luck in several places scattered throughout Crook, Deschutes, Jefferson and Lake counties.

Where to dig

Rockhounding areas were first mapped in the 1960s, when a few of the sites were maintained by local chambers of commerce. Four years ago, the Forest Service, BLM and the Prineville-Crook County Chamber of Commerce joined together to update the map, complete with Global Positioning System coordinates, a briefing on local geologic history and the “rockhound’s code of ethics,” which includes guidelines on how to hunt for rocks without harming the environment.

The rules for using sites like Maury Mountain, Dendrite Butte and Congleton Hollow, all southeast of Prineville, or Bear Creek or Hampton Butte, just north of the Deschutes County border with Crook County, are fairly simple. Gordon said rockhounds are free to use shovels and take home their finds, but cannot use any mechanized digging equipment or blast through the rock.

“The thing is (taking) reasonable amounts — what we’re talking about is personal collecting,” she said. “This is not for the commercial operator that wants to work the product and sell it. We’re talking about recreation, going out with the family for personal collection.”

And often, Gordon said people can find all kinds of unique rocks for their collections without any equipment at all.

“I know folks like to dig around with shovels, dig holes, but I’ve actually found some of my best pieces just walking around in the spring on the slopes in the forest and on BLM land,” she said. “You can do surface collecting anywhere.”

Though public lands are popular destinations for rockhounds of all experience levels and interests, some opt to do their digging at places like Richardson’s Recreational Ranch in Madras. The 17,000-acre ranch includes about 4,000 acres designated for rockhounds hoping to find their own thunder eggs. Visitors pay by the pound for whatever they take away.

Norma Richardson, who runs the ranch with her husband and son, said that after more than 30 years in business, tens of thousands of tourists still pass through every year.

“I think every grandparent in Deschutes County has brought their grandchildren in to dig around … where else can you take a family of four, go out for the day, take a picnic and get to play in the dirt, which the kids love?” she said. “And you have something to take home and show for it.”

The rock business

Other rockhounds — perhaps those who don’t find success on their own digs — opt to shop for a souvenir at a place like Elkins Gem Stones, which is stocked with rocks collected locally and from all over the country.

“It’s amazing, the wide spectrum of people who come in,” Elkins said. “I have people who come in and they want a thunder egg, and you show them the thunder eggs and they leave happy. And then there’s the people who want to know all about everything.”

Perhaps the busiest time of year is in late June and early July, when three rockhound gatherings are held in Prineville, Madras and Sisters. Rebecca Buss, of Culver, who helps coordinate the Prineville Rock Hound Powwow, said the event has been held for more than 60 years and brings in people from as far away as Switzerland. The Prineville event, scheduled for June 26 through June 29 at the Crook County Fairgrounds, includes dozens of vendors who show and sell their rock-related wares.

Year-round, the rockhounds are a boost to Crook County, spending money in cafes and shops, and spreading the word about what the county has to offer, said Brandi Hereford, executive director of the Prineville-Crook County Chamber of Commerce. She said the chamber gives out hundreds of the rockhounding maps each year.

“It’s a large number of people who come in for (the map,)” she said. “They’re very specific: ‘I’m here to rockhound, where’s the map?’”

Elkins said her business has gone up considerably in the past few years.

Though Crook County attracts visitors for a variety of outdoor activities, she said rockhounding will likely remain a top draw as long as people are curious about nature, and want to get outdoors and see what they can find.

“Some people are here for specimen pieces, and other people are here for stuff they can cut into jewelry,” she said. “There are a wide variety of people, but almost everybody likes the outdoors. They appreciate nature and things like that, and just want to go out and enjoy it.”

And more importantly, Elkins said, all good rockhounds share a love for a material others might ignore.

“They just like rocks,” she said. “And it’s only a good rock if you like it.”

Four rocks you can find around here

Rockhounds can find a variety of rocks in Central Oregon, from shiny pieces of obsidian to agate, jasper and perhaps the most popular rocks, thunder eggs. The unique rocks were created by volcanic activity that took place up to 50 million years ago. For a map of Central Oregon rockhounding spots, see Page A7.

Thunder eggs: The ball-shaped rocks are usually a bit larger than a baseball. On the outside, thunder eggs are drab and bumpy, but on the inside, they are often filled with crystals, agate, jasper or a powdery calcite. Some thunder eggs, however, are empty. Popular hunting spots include Whistler and White Fur Springs in the Ochoco National Forest northeast of Prineville.

Obsidian: Usually black in color, obsidian is a volcanic glass with a shiny surface. The rock sometimes appears in other color types, which are referred to as gold sheen, silver sheen, fire sheen, rainbow, midnight lace, double flow and mahogany. It can be found around Glass Buttes, in Lake County just over the south Deschutes County border.

Agate: Often found in fractures in volcanic rocks, agate is a translucent type of quartz. In this area, agate is often light in color. Some have distinctive swirled designs and might appear to contain plants under the surface. Good spots to find agate include Fischer Canyon and Maury Mountain, both southeast of Prineville, and the North Ochoco Reservoir, located on BLM property east of Prineville.

Jasper: Another variety of quartz, jasper can occur in several colors, typically red and yellow but sometimes green, tan, brown or purple. Rockhounds consider “picture jasper,” with its designs on cut surfaces, the most valuable type of the rock. Local jasper hot spots include Fischer Canyon and the North Ochoco Reservoir.

Source: U.S. Forest Service; photos courtesy Oregon Department of Geology and Mineral Industries