The largest diamond ever found was 3,106 carats in the rough and originally weighed just under one and a half pounds. The Cullinan was cut into 9 major stones and 96 smaller stones. The Cullinan Diamond was the largest gem-quality diamond ever discovered, it weighed a whopping 3,106 carats, that is equivalent to one and one-third pounds. It was found in 1907, and here's how. A superintendent thought his co-workers were playing around by putting a large piece of glass on the top edge of the mine pit. Before picking it up, he looked around to see if anyone was waiting for him to fall for their trick, he did not see any one, so he picked up what he thought was glass. This piece of glass turned out to be the world's largest diamond. The Transvall Government bought the diamond, which was presented to King Edward VII on his 66th birthday. The rough diamond was insured for $1,250,000. when it was sent to Asscher's Diamond Company to be cut. A heavy steel blade shattered on the first attempt to cut the diamond. On the second attempt the diamond fell apart- - - exactly as planned. It was reported that the diamond cutter fainted shortly after