Billions of years in the making, diamonds are one of nature’s most wondrous and precious gifts. After being formed in the earth under immense pressure and heat, precise cutting and polishing bring out their incomparable beauty. While one could feast her eyes on beautiful diamonds at virtually any jewellery store, only the most perfect ones – think 100-plus carats and incredibly rare colours – reach stratospheric prices at auction. To pay tribute to April's birthstone, we take a look at fourteen breathtaking diamonds that have come to Sotheby’s.