Lauren Fensterstock is a sculptor and installation artist whose sparkling, intricate creations look like secret treasures stolen from a gothic witches’ cathedral or like the charred remains of a fairy swamp. Made from materials including glass, vintage crystal, quartz, obsidian, onyx, hematite, shells, sand, plexiglass, paper, charcoal, and wood, her most recent installations—like the one on display at the Smithsonian American Art Museum’s Renwick Gallery in D.C. earlier this year—are enormous, completely black, and suck all the surrounding light into the curves and edges of...