Mark Heidebrecht has collected rocks ever since he took a geology class at McPherson College.

"The general population is unaware of how pretty rocks are," Heidebrecht said.

Now, decades later, he will part with a few of his treasures at the McPherson Gem and Mineral Club’s 27th annual Swap and Sale.

"For the first time ever, I'm going to have a table and sell some things," Heidebrecht said.

Heidebrecht's rock collection includes specimens from around the globe — and many he has dug himself.

"I do have to range far and wide to get some of this stuff," Heidebrecht said. "I do enjoy collecting it because it's kind of like a treasure hunt."

When he goes to other states on rock-hunting trips, Heidebrecht focuses on looking for his favorite stones — agates — buried in pits, fields and roadways.

"They're pretty hard to find, in my opinion," Heidebrecht said.

It takes sharp eyes to find the rocks that may be a dull gray or brown on the outside, but have a spectrum of blue, brown, green, red and other colors inside.

"They're very colorful and there's an endless variety of them," Heidebrecht said.

After finding the agates, Heidebrecht slices them and cuts them into a rough shape to polish into cabochons — a stone with a flat bottom side and a rounded top side.

"It's an art I had to learn, but I think I've got it down — at least to my satisfaction," Heidebrecht said.

Heidebrecht attaches a small dowel rod onto the slice of agate using wax in order to move it around more easily when grinding it into shape.

"It gets a real good grip on the rock so you don't have to be trimming the rock and your nails at the same time," Heidebrecht said.

It takes a week to polish the stones, using progressively finer grit at each stage and washing them completely between each step.

"It's a very messy hobby," Heidebrecht said.

While he stills enjoys being a rockhound, Heidebrecht said he is ready to thin out his collection.

"I've got lots of inventory," Heidebrecht laughed.

Heidebrecht will bring rocks at various stages of polishing to the Swap and Sale — an event he said always draws the interest of both adults and children.He hopes to aid a budding rockhound in starting their own collection.

"I'm going to have rough rock and I want to price it cheap for the kids," Heidebrecht said.

The McPherson Gem & Mineral Club’s 27th annual Swap & Sale will be held from 9 a.m. to 6 p.m. Friday and Saturday and 9:30 a.m. to 3 p.m. Sunday at the 4-H Fairgrounds, 710 W. Woodside in McPherson. Admission is free.

Vendors will bring a variety of rocks, minerals, fossils, crystals, gemstones, handcrafted jewelry, home decor, lapidary work and more. The event will feature door prizes, rock and mineral identification, concessions and an auction at 7:30 p.m. Saturday.

For more information, visit https://mcphersongemandmineralclub.org.

Contact Patricia Middleton by email at pmiddleton@mcphersonsentinel.com or follow her stories on Twitter at @MiddleSentinel.