Natural fancy blue diamonds are completely natural and are usually classified as either gray-blue or green-blue. The color in gray-blue, grayish blue, blackish blue or black-blue colored diamonds is caused by the presence of minor amounts of boron in their structure. Green-blue or greenish blue (teal) colored diamonds usually contain nitrogen impurities in aggregate form.
The most famous of all natural colored blue diamonds is the 45.52 carat 'Hope Diamond'. The Hope Diamond was originally 112.25 carats when it was purchased in India and sold to the French King Louis XIV. $569,000 is the most paid per carat for a blue diamond (for a 4.37 carat diamond sold in 1995 at Christie's for $2,486,000).
Natural fancy blue diamonds range from the pale to brilliant blue diamonds and intense blue diamonds.
Natural fancy blue diamonds come in all cuts, including princess, emerald, asscher, oval marquise, pear, radiant, heart and cushion, though round natural fancy blue diamonds are the most common.
