Co-owner Tay Herbaugh jokes with a customer at the Bloom Bums Crystals & More stand inside Keg and Case Market. (Leila Navidi, Star Tribune/The Minnesota Star Tribune)

Tay Herbaugh has rocks in their pockets. In one, a smooth green opal (to help feel emotions but not be ruled by them). In the other, merlinite (for spiritual awareness).

At home, there's a green calcite (for growth) near the potted plants. By the bed sits amethyst (for good dreams). And in Herbaugh's car, there's a piece of selenite (to banish negativity).

"I like to call it the Mr. Clean Magic Eraser of the aura," Herbaugh said about the cloudy white columns of crystal. "The ultimate thing that crystals are all about is connection, compassion, understanding."

Herbaugh, who uses they/them pronouns, is among a growing number of people putting faith in these minerals as a way to seek connection, clarity and peace of mind. A recent study by Springtide Research Institute, which focuses on understanding the spiritual needs of young people, found that 44% of 13- to 25-year-olds use crystals in spiritual ways, and that 20% do so on a weekly basis.

Their rising popularity is apparent in Minnesota, where old-school rock stores like Richfield's Enchanted Rock Garden are drawing new shoppers interested in all things metaphysical. Local spas are putting in quartz saunas. And even chains like JoAnn Fabric and Crafts sell packaged stones for sale near their counters.

In Bloomington, a new outpost of the Crystal Rock Healing store chain is set to hold a grand opening party May 20, with card readers and crystal healers.

"I'm amazed how many women [ages] 30 to 60 are really into crystals, and decorating their house with them so they bring in the energy they want," said owner Cindy Schmitz.

A different form of faith

Herbaugh, who was raised Catholic, found crystals after they sought out "alternate forms of faith."

"When I started realizing I was gay, everything about being Catholic was like, 'Shame on me.' " Herbaugh said.

Reading about crystals led Herbaugh to believe that the stones help with self-discovery. They now sell crystals and other metaphysical products at the Bloom Bums stand at the Minneapolis Farmers Market Annex and other places with their partner in life and business, Ben Polzin.

"A lot of people are looking for connection," Herbaugh said. "They're looking for a new way of figuring out themselves, learning about security and love."

When people ask how the stones "work," Herbaugh explains that the atoms that make up everything are always vibrating. And that as the vibrations in our bodies interact with the crystals' vibrations, energy can shift.

"It helps you understand you better," they said.

While there are no scientific studies backing crystals' healing properties, academics are looking into the science of "vibes."

At the University of California, Santa Barbara, a brain scientist and philosopher team has looked into what we can learn from how the vibration of different things sync up, from groups of fireflies lighting up together to neurons firing in the brain. They concluded that vibrations, resonance, "are the key mechanism behind human consciousness."

Lately, Herbaugh and Polzin's customers have been asking for stones to help with stress and anxiety, Polzin said — as well as crystals connected with setting boundaries and self-confidence, like black tourmaline or carnelian.

Middle Age texts to TikTok

Rock hounds still stop in at the Enchanted Rock Garden, which has been in business for 30 years. But the staff has noticed a distinct shift: A growing number of customers are now seeking stones to connect with on a spiritual level, said Ginny Shaver, who makes much of the store's jewelry.

Recently, people have been asking for moldavite, which has been featured on TikTok. The pricey green crystal ($350 buys a small piece) is supposed to help people make "life-changing decisions," she said.

While crystals are currently trendy, humans have been fascinated by them and seen them as spiritual objects for centuries, according to research by Stanford medieval scholar Marisa Galvez.

"Crystal's transparency, hardness and exceptional ability to carry light among precious metals and stones made it a stone generally held to symbolize purity of faith or innocence" in the 12th and 13th centuries, she wrote in a 2014 paper. Medieval poets also used crystals to depict love and desire, she wrote.

Turning inward

Minneapolis life coaches Lana Brooks and Karina Muller, who run a business called HeartCentric, use amethyst, quartz and other crystals to make pendulums, a centuries-old spiritual practice that's also seeing a resurgence.

"Our mission right now is to help people to tap into their intuition with the help of a pendulum," said Muller.

Pendulum users first dangle the stone on a chain and ask it to show them "yes" or "no" with movements. Then, they ask a series of yes or no questions. The stone moves through the users' imperceptible movements, called "ideo-motor reflexes" that Muller said can reveal their subconscious knowledge and insights.

Looking inward for clarity and answers is very popular right now, and part of the reason crystals and pendulums are on the rise, Brooks said.

"What the pendulum does is it really allows you to connect with yourself on a spiritual level, to gain the clarity that you're seeking for your life, to gain wisdom, to gain knowledge, to just check in with yourself," Brooks said.

"These tools are for everybody. There's no religion attached to it. It's really about opening your mind to being a part of something bigger than yourself."