Sales of rough from Mountain Province’s Gahcho Kué mine in Canada dropped in the first quarter amid slow demand and weak prices. Diamond sales fell 31% year on year to $66.1 million for the three months ending March 31, Mountain Province said last week. Sales volume slipped 2% to 938,310 carats, while the average price plunged 29% to $70 per carat. The decrease is the result of a prolonged slowdown in the diamond market caused