(IDEX Online) - The largest white diamond ever auctioned sold yesterday for $21.9m at Christie's Magnificent Jewels sale in Geneva.The 228.31-ct G/VS1 pear-shaped gem, called The Rock, beat its low estimate of $20m, but fell short of the $30m high estimate.The record auction price for a white diamond remains with a 163.41-ct D/IF Type IIa rectangular cut-cornered diamond, which sold at Christie's Geneva in November 2017 for $33,701,000. It was previously part of an emerald and diamond necklace from Swiss luxury jeweler de Grisogono, The Rock (pictured), was mined and polished in South Africa over 20 years ago and was worn as a Cartier necklace by its previous owner.Another highlight of the sale, the cushion-shaped, 205.07-carat, fancy-intense-yellow Red Cross diamond, sold for $14.3m. An undisclosed part of the sale revenue will be donated to the International Committee of the Red Cross.