Jean Schlumberger. Among the cognoscenti he’s considered the greatest of 20th-century jewelers—a purist who mixed precious and semiprecious stones, thought diamonds a bit vulgar, and loved the less common peridot and moonstone. His genius was in his designs. Schlumberger could be inspired by clients, especially an imaginative and moneyed client like Rachel Lambert “Bunny” Mellon. Glittering in Toronto, Schlumberger showstoppers from Mellon’s collection are on loan from the Virginia Museum of Fine Arts. —L.J.