An 18.04-carat Colombian emerald once owned by the famed Rockefeller family sold at auction Tuesday for over $5 million.The emerald was originally purchased from Van Cleef & Aprels as a part of a brooch by John D. Rockefeller in 1930. The brooch was a gift for his wife Abby Aldrich Rockefeller. After his wife's death, Rockefeller asked jeweler Raymond Carter Yard to disassemble the piece, who in turn helped to showcase the stone's impeccable clarity. When Yard returned the emerald, he had mounted it on a diamond and platinum setting. The ring passed through several other owners through the years, but never lost its majestic look and feel. According to Christie's, the emerald was expected to go for $4-6 million Tuesday. The stone is the highlight of the auction house's 'Magnificent Jewels' sale. Famed jeweler Harry Winston was the winning bidder, putting up $5,511,500. Breaking it down, that equates to $305,000 per carat.