The rocks on Chuma Mbalu-Keswa's table, she admits, are not exactly eye-catching. "They look uninteresting, I know," she writes in a note penciled neatly on the back of a departmental announcement.
"But," the note continues, "look at the photographs!"
Lined up at the table's edge are five rugged chunks of kimberlite. They are blue-gray—sooty, which makes sense since they were lately rescued from a coal mine in southwestern Pennsylvania. Flecks of mica shine through the grime of their surfaces, glittering like nightclub chic.