MARTINEZ — Ann and George “Matt” Matthews go by the adage “Rockhounds never die, they just slowly petrify.”

In the couple’s front yard sits a large blue rock with a story. In fact, the Martinez residents who have been collecting rocks for nearly 40 years say that every rock tells a different story. The Dumortierite in the front yard weighing 832 pounds takes the couple back to Arizona in the 1970s, the time they first began gathering rocks.

“It was a trick getting that in the back of the truck,” said Matt Matthews. “We couldn’t break it so we brought the whole thing home.”

The Matthews’ were on a field trip with members of the Contra Costa Mineral and Gem Society, known to members as the “Rock Club.” It took a group of men to haul the huge mineral and one of the men got caught in a cactus while carrying it to the truck.

“It’s not just a hobby,” said Ann Matthews. “It’s a disease — but a good one.”

The couple, married for 57 years, took camping trips with their children and other rockhounds to sites such as Black Rock Desert. Besides Quartzsite, Ariz., “the Rock Capital of the World,” the Matthews have been on rock hunting trips to Oregon, Washington, Nevada and Utah. Visitors to the Matthews’ home are at once greeted by the “oddball” rocks — a Tufa, a type of limestone, shaped like a poodle’s head and a river rock found in Arizona that resembles a panda’s face.

The couple has also created art from the rocks they collected. Ann Matthews formed flowers out of pieces of rocks and crystals and artfully glued them on picture frames while her husband shaped several varieties of rocks into smooth spheres using a rocksaw and a machine he built himself. Most rocks are organic pieces of artwork; thin pieces of mahogany obsidians are considered to be “nature’s glass,” said Ann Matthews.

When their children were very young, Ann Matthews said a cousin encouraged them to visit Patrick’s Point State Park north of Eureka.

“She said, ‘There’s agate over there,’ ” said Matt Matthews.

“We’d never heard of agate,” Ann Matthews said.

Since then, the couple has amassed countless agates, obsidians and petrified wood found in various “hot spots” in Northern California and beyond. They said they wouldn’t have known about these sites had it not been for the Rock Club.

“The rocks are souvenirs — the bonus part of our trips. But the real gems are the nicest people you’ll ever meet,” said Ann Matthews.

One of the members, Harry Nichandros of Concord, who always loved collecting rocks since childhood, once had a hard time identifying them. He took geology courses in college then joined the Rock Club.

“There are people in the club with different specialties,” said Nichandros, the rock show’s chairman. “One who can identify crystals like a master.”

Members gather on the second Monday every month to listen to speakers such as geologists and mineralogists talk about various topics.

“By being in the club talking to people, I learned a lot about rocks,” Nichandros said. “It’s enhanced my knowledge about geology as well as precious stones, agates, jaspers, beautiful pieces to be used in jewelry.”

The work of lapidary artists, who form mineral and stones to make jewelry and other decorative items, is a facet of the gem world that’s quite fascinating, Nichandros said.

Like the Matthews, Nichandros said as far as local sites, he’s enjoyed going up to Davis Creek in Northern California, although there aren’t too many locations that are open to the public like before as property owners have closed out areas formerly explored by rockhounds. The Rock Club helps its members find places that are accessible to the public or where rockhounds may pay a fee to explore and gather rocks.

Nichandros said he believes rocks and minerals are still abundant and there are still plenty of treasures for rockhounds to discover.

“As the earth changes, there are new sources of rocks being formed all the time,” he said.

While on a trip to Diamond Peak in Arizona, Nichandros said a helpful ranger guided him toward various gem trails where he discovered some geode, spherical masses of mineral matter, which sometimes have crystals in the center. He’s also found fossilized clam shells in Orinda that lead him to learn about the geological history of the Bay Area.

Nichandros has also looked for rocks in Grass Valley and Wall Canyon, Nevada. He once picked up Serpentine along the side of a Cloverdale road in Sonoma County. He remembers while on one of his first field trips years ago to Valley Springs, he found people were collecting buckets full of agates, a kind of quartz. He eventually bought a rare World War II ammo bag to gather rocks in.

“There’s a story in just about every rock and how it formed,” Nichandros said. “If you study a rock, it will tell you where it came from.”

As a sixth-grade science teacher at Pleasant Hill Middle School, Mary Hanjes likes to collect rocks to share with her students.

“I teach Earth Science so they can learn how amazing the earth is,” said Hanjes, a Walnut Creek resident.

She joined the Rock Club a few years ago to learn more about the different specimens as well as discover places to collect rocks. She visited Pala, near San Diego, on her own where she found some tourmaline along the ocean view mines.

At the Contra Costa Mineral and Gem Society’s rock show, Hanjes will display her students’ favorite rocks along with information about each rock written by the students.

“Kids have so little interaction with things outside these days,” Hanjes said. “It’s nice to tie this back to the earth. My students love rocks. They’re amazed by these rocks that came from the earth. They would bring in their own rocks to show me. The rocks represent something good to them. For them, they’re more than just rocks, but good memories.”