A complete cave bear skeleton, a pair of 10,000-year-old walrus skulls and one- of-a-kind trilobite fossils are among the many surprises in Dave's Down to Earth Rock Shop. Despite the free museum in the basement showcasing Dave Douglass' collection and a first floor shop with myriad offerings, the Main Street storefront often goes overlooked.

Dave's brother, James Douglass, and sister-in-law, Susanne Ali, have run the store for eight years. While it doesn't have the buzz of other Chicagoland hotspots like the Field Museum, Ali says that between field trips for grade schoolers and college classes, visits by collectors and tourists and figuring out what new things to buy, there are no ordinary days running the store.

"We consider ourselves kind of like an adoption agency," Ali says. "We take something and treasure it for a little while and then pass it on to somebody who's gonna treasure it even more, and hopefully for a long time."

There's no shortage of treasure in the store. From bright aquamarine crystals the size of a roll of quarters to a lively set of fossilized crabs and even handmade jewelry, almost everything in the store is unique, according to Ali.

The shop's yearly trip to Tuscon, Arizona is its largest buying trip. Dougless and Ali travel to a rock and mineral show there and buy inventory, planning ahead to the holiday season.

More than just the shop owners benefit from these trips. The Northwestern Geology Department looks forward to its annual trip and those like it. Dave's is an anomaly because of its location in a suburban, relatively eastern city, says Brad Sageman, a geology professor at Northwestern and long-time Evanston resident. According to Sagement, it's the only shop the geology department uses when they need presents for retirements or tenures. When the department relocated to the Technological Institute from South Campus three years ago, Sageman says, they used Dave's to help decorate their new space. The most notable piece they bought is the slab of Moroccan fossils mounted on the wall of the department's seminar room.

"I called up Susanna and said, ‘Next time you go to the Denver Gem and Mineral Show, keep your eyes out for a really impressive fossil slab, because we want to buy it to mount on the wall,'" Sageman says. "They sent me a picture, and it was killer. They regularly have access to stuff like this. It'd be much harder to do something like this if they weren't around."

Dave's also benefits from proximity to the university. Steve Jacobsen, a geology professor and researcher in the mineral physics laboratory, says he takes his higher level classes on field trips there every quarter. In his lab, he uses a method called Raman spectroscopy to analyze minerals that Dave's wants to identify or confirm before selling. The most notable instance of this, Jacobsen says, is a blue walrus tusk the shop once bought. He and his colleagues identified the blue mineral as vivianite growing in the walrus tusk. Jacobsen's lab also confirmed the slab of Moroccan fossils purchased by the university was authentic.

"It's kind of cool that the same system we do all this science with can be used for a community," Jacobsen says. "They don't pay me. It's me supporting a local business that I really like and appreciate. I grew up in Colorado and was able to take students on field trips in the afternoon. Here in Chicago, we go to Dave's Rock Shop. It's the best place to see a big diversity of rocks and minerals locally."