Red Diamonds These are the rarest diamonds in the world. Basically, pure red diamonds do not exist or rather have not been found so far. The available ones are fancy purplish-red or brownish-red. The red color in combination with other high-quality 3Cs makes them priceless. The two famous red diamonds ever sold are the Moussaieff Red and the Hancock Red Diamond. These diamonds are among the most famous diamonds ever mined. The current value could be extraordinarily high.