The Spiders (24-7, 13-3 Atlantic 10) won their fourth straight game and have already clinched a first-round bye heading into next week's conference tournament. Cedrick Lindsay pitched in with 11 points.
Richmond went into halftime with a 37-30 lead, then dominated the second half, leading by as many as 17 points. Lindsay gave the Spiders their largest margin when he made a free throw after being fouled on a steal.
The Dukes (18-11, 10-6), who have lost four of their last five games, never got closer than 12 points the rest of the way.