FRESNO, Calif. - In an age when many people crave easy living, there are dozens of folks who go out of their way to put themselves between a rock and a hard place.

These adventurers are rockhounds - a hardy bunch who love to explore the nation's geologic landscape in search of treasures from the earth's crust that are interesting, beautiful and sometimes valuable.

"All you need to get started is a strong pair of legs," says Bobby Cook, 72, a retired railroad conductor and president of the Fresno, Calif., Gem and Mineral Society.

Cook says one of the fascinating things about rock collecting is the opportunity it provides to get outdoors and learn about the earth's surface and how it was formed. Although learning how to identify interesting rock and mineral specimens takes experience, he says veteran members of gem and mineral clubs are eager to share their knowledge with newcomers to the hobby.

Clubs are located in Fresno, Mariposa, Hanford, Lemoore, Visalia, Porterville and Coalinga. The organizations have members who lead field trips to rock collecting sites in and outside of the Valley. Most of the groups also provide members with access to expensive equipment used for cutting, carving and polishing stones.

A good way to get an introduction to rock collecting is to attend a gem and mineral show presented by one of the clubs.

The California State Mining and Mineral Museum, in cooperation with the Mining Museum Association and the Mariposa Gem and Mineral Club, will present a mineral and gem show next weekend at the Mariposa County Fairground.

At 2 p.m. Saturday, there will be a demonstration on using metal detectors to find gold, and at 10:30 a.m. Sunday, visitors can learn how to make wire-wrapped jewelry. Geode-cutting demonstrations will be held both days, and more than 25 vendors will have gems and minerals on display. There also will be craft activities and a scavenger hunt for children.

Rockhounds come from all walks of life. Johnnie Sherlock, 69, of Coalinga, Calif., is a retired registered nurse. Wayne Gilkey, 66, of Hanford, Calif., owns a paving company, Rob Milner, 50, of Exeter, Calif., is a Tulare County agricultural inspector, and Don Vieira, 72, of Visalia, Calif., is a retired community college agricultural science and mechanics instructor.

"I just like to hunt for rocks," says Sherlock. "I also like working with gemstones and I've made a little bit of jewelry."

Gilkey discovered rock collecting at age 5, when he went to work with his father and saw a bulldozer unearth a petrified log.

"I found a piece of that log that looked just like an alligator's head," he says. "I still have it. Most of what you find, you throw away, but every now and then, you find a keeper."

Gilkey says nice rocks, when cut and polished, produce fond memories and make excellent gifts.

"You like to remember where you found it and the fun you had finding it," he says.

Although the central San Joaquin Valley is best known for its agriculture, the region is within easy driving distance of some interesting rock collecting sites.

Gold still can be found in the Mariposa area, says Dusty Luker, 56, a retired Army veteran and president of the Mariposa Gem and Mineral Club.

"We like to go panning in the rivers," he says. "I've always liked the outdoors and it's good to get out with people who know a lot. We're always learning."

For example, jade can be found in the hills east of Porterville, Calif., and there are places near Coalinga, Calif., that are excellent for finding fossils, Milner says.

"Porterville jade is some of the greenest and best in North America," he says.

Vieira says collectors also like to venture east of the Sierra to look for interesting rocks in the Mojave desert.

"When we're collecting, we must abide by a code of ethics," he says. "We don't go on private property without permission. We don't use dynamite and we don't collect on federal and state land where it is prohibited."

On public land where rock collecting is permitted, members must obey Bureau of Land Management regulations. It's against the law to remove arrowheads and other materials from prehistoric cultures without an archaeological permit or to gather vertebrate fossils without a paleontological permit.

The collection of petrified wood is limited to 25 pounds a person per day, while the amount of rocks, minerals, gemstones and invertebrate and plant fossils of non-scientific importance cannot exceed the capacity of a daypack.

John Pereira, 50, who owns a jewelry store in Lemoore, became a rockhound because of his interest in creating custom jewelry.

"Cutting stones led me to want to find my own stones," he says. "I didn't realize what material was out there locally. You can find agates that cut and polish nicely. The big thing for me is I can cut the stones the way I want them."

Collecting rocks in the field does not require much equipment. All you need is a pick hammer to break up soil or rocks, safety goggles, a shovel and a container to carry home specimens.

More expensive equipment is required for cutting, polishing and shaping rocks.

"You can easily spend up to $10,000 on equipment," Milner says. "That's where the clubs come in. They have equipment people can use."

Many rockhounds enjoy cutting geodes. These globular stones often have interesting patterns inside.

"I have one rock with a perfect picture of a bird in flight," Vieira says. "I enjoy seeing what's inside of a rock. You never know what you're going to find."

It's this thrill of discovery that keeps rockhounds on the trail for interesting specimens.

"The natural beauty inside a rock can't be duplicated by man," Milner says. "Rock collecting enables me to experience the elements of nature in the desert or mountains. I can pick up a rock, bring it home and cut it open. Then you take that beauty and turn it into an art form. It's showing Mother Nature at her best."