Look at Erik Rintamaki’s rock collection under the white light of a 60-watt bulb or with sunlight streaming in the window, and you might nod politely. A lifelong rock picker, the Michigander has gathered a smattering of shapes, sizes, and colors. The rocks with rounded edges—many of them small enough to fit in your palm—tell long stories of ancient, grinding ice, and the relentless movement of waves and sand. Many are unassuming shades of gray, white, or pink. Mottled or flecked with black, the rocks are pretty, he says, like…
