The DeYoung Red Diamond is one of the largest known natural fancy dark red diamonds. It is a modified round brilliant cut diamond that has a clarity grade of VS-2 and weighs 5.03 carats. The diamond was acquired by S. Sydney DeYoung, a Boston jeweler, as part of a collection of estate jewelry in which it was wrongly identified as a garnet. It was gifted to the National Gem Collection by Mr. DeYoung in 1987.
Red Diamonds - ~$ 2 million per carat Though all colored diamonds are incredibly rare, none are more so than the red diamond. Less than 20 exist today and most weigh less than half a carat, however there are three that weigh over 5 carats with the biggest being the Moussaieff Red (5.11 carats).
A former record breaker in the color diamond world, The Hancock Red is a 0.95-carat Fancy Purplish-Red stone. The diamond was originally purchased at auction in 1956 by Warren Hancock for $13,500. When it was put up for auction again in 1987, it sold for $926,000/carat. The previous per carat record for a diamond was $127,000/carat!
The-Moussaieff-Red-Diamond The price is $7,000,000.00. This astonishing gem is color red and has a definite size of 5.11 K or 1.022 grams. It has a cone shaped precisely cut that is appraised as striking red according to the intense observation and study of the American Gemological Institute. This gem is a little bit smaller compare to other highly valued diamond but according to the AGI, so far, it is the largest red diamond ever appraised.