After school on a Wednesday, 45 elementary school students clustered in a classroom at Aspen Academy, eager to learn about an unlikely subject — rocks.

“This one’s kind of smelly,” Michelle Cauley, a third-grade teacher said while holding up a rock. “It’s used to make medicine and fertilizer.”

As the kids tried to determine which rock Cauley, the club founder, was describing, the students whispered, sniffed the jagged, yellow rock and wrote down observations.

“It smells like the swamp by my dad’s house,” one boy said.

“Is it sulfur?” a girl asked.

She was right. The room then puzzled over clues describing fluorite and granite. It was a typical afternoon for the Aspen Academy Rockhounds, a club of 60 kids with a passion for studying and collecting rocks.

Parents and students at the Prior Lake charter school say it’s not just the topic that’s enthralling, but the enthusiasm Cauley brings to every meeting.

“They’ve got a passionate leader in Mrs. Cauley,” said Noah Levie, a parent of two Rockhounds. “She makes it relevant to them.”

His daughter agreed.

“Mrs. Cauley makes everything fun,” third-grader Mandy Levie said.

The club, which started last year with eight members, meets three days a week to accommodate all the interest. It’s growing so fast that next year, it may meet more often.

Cauley is thrilled at the club’s popularity and said it was born out of her lifelong passion for geology.

“I love it,” said Cauley, who began collecting rocks when she was 5. “It’s a dream come true.”

Collecting and trading

Each week, students learn a geology lesson and are introduced to the “Rock of the Day.” They also get to take home a sample of that rock.

There are currently two levels of the club: beginners and experts. Beginners, who joined this year, learn rock basics, including layers in the earth and geologic processes. Experts, who were in the club last year, focus on minerals, including their structure. They review mineral-related legends and myths and talk about jobs in the geology field.

But for both groups, the most exciting part is likely trading, which Cauley said is “a huge aspect” of the group’s appeal.

Students open up their clear plastic rock boxes, the kind sometimes used to sort beads or embroidery floss. The boxes overflow with rocks of all colors and textures — granite or lavenderite, fuschite or gypsum, with the occasional fossil thrown in. Some kid have double-decker boxes or cases designed like suitcases.

“You can get rocks that you really want for stuff that you don’t want,” explained Caiden Winick.

The ability to collect and trade is important to kids, said Stephanie Peterson, an Aspen Academy third-grade teacher.

“I think they really like collecting things — third-graders really get into it,” she said.

Though most members are in third and fourth grades, the club is open to grades three through eight.

It is also a hit because it allows kids to “identify things in the world around them,” Cauley said.

“Rocks are actually used in our daily lives, like our toothpaste has fluoride in it and our walls have gypsum in them,” fourth-grader Maddie Hoyd said.

Bringing people together

Cauley went from collecting rocks as a kid to studying geology in college.

In her spare time, she volunteers at a Minneapolis rock store that’s “very kid-friendly,” she said. The store sponsors field trips to unearth fossils in places like northeastern Minnesota and Iowa, and she’s gone on them in the past with students.

“It’s still a treasure hunt for me,” she said. “This is made of nature, this is coming out of the ground. What else can I find?”

Cauley said leading the kids has pushed her to do more research and helped her bond with students.

“I’m able to connect with them outside of academics,” she said. “I’m getting to share a little more about my interests, and they’re getting to share as well.”

An affinity for rocks has had a neat side effect for a few students: It’s brought them closer to family members who are also rock-lovers, Cauley said.

Cauley anticipates that next year she may have to spend four or even five nights a week with the Rockhounds. She wants to expand the club to three levels and have officers, fundraisers, a newsletter and even T-shirts.

“I want to take it as far as the kids want it to go,” she said.

Some kids said Cauley has inspired a deep, lifelong interest in geology.

“I think we’ll always love rocks,” Mandy Levie said. “Geology is awesome.”