The Pink Star diamond is the most valuable gemstone in the world as of 2015, with an estimated value of $83,187,381 and the highest possible color and clarity rating. This diamond weighs 59.6 carats, or 11.92 grams, which is about $1,395,761 per carat.
Once known as the "Steinmetz Pink," the Pink Star diamond is the largest known vivid pink diamond in the world. This incredibly rare diamond was mined in 1999 by De Beers in Africa, and once weighed 132.5 carats in the rough. Over two years, this gemstone was carefully cut and polished by Steinmetz Diamonds.
Originally the Pink Star was estimated to sell for more than $60 million, but it sold for $83.2 million to Isaac Wolf after he outbid three others. However, Isaac Wolf defaulted on the purchase, and Sotheby's retains it in its inventory.