Harry Oppenheimer, former head of the world’s leading diamond and gold mining operations and South Africa’s best-known Thoroughbred breeder and owner, died Aug. 19 in Johannsburg. He was 91.Just last year, Oppenheimer was on hand to personally receive seven awards at South Africa’s annual Equus Awards. With his wife, Bridget, he raced 1999 South African Triple Crown winner Horse Chestnut. The homebred son of Fort Wood won his only North American start, the Jan. 8 Broward Handicap (gr. III) at Gulfstream, but subsequently fractured a splint bone and suffered suspensory damage in his left front leg. He was retired and stood this year at the Hancock family’s Claiborne Farm near Paris, Ky.Oppenheimer was the retired chairman of Anglo American Corp. and its sister, De Beers Consolidated Mines Ltd., the latter controlling 80% of the world’s global diamond sales.He began Mauritzfontein Farm in 1946, on the site of De Beers remount depot. Since that time, the stud has consistently produced top South African runners.