If you have the slightest idea about blue diamonds your first association concerning them would normally be The Hope Diamond. Indeed, this the most famous blue diamond in the world, the replica of which you could see in iconic Titanic movie. And that was the trigger to set the trend for them. Truly, blue diamonds are one of the most sought after (after pink, of course), however the most expensive, too. That is why for most of women they remain rather a hope than a reality. Still there is some more detailed information about these beautiful gems:
Natural blue diamonds are exceptionally rare. Larger blue diamonds have achieved record prices at auction in recent years. In October 2010, a 10.95 carat fancy vivid blue diamond, the “Bulgari Blue,” broke auction records selling for $15.7 million at Christie’s. In October 2011, a 6.01 carat fancy vivid blue diamond ring fetched $10.1 million–setting a world record price per carat for diamonds of its type sold at auction. Blue diamonds great and small are priced according to rarity, and it is not uncommon to find stones under .25 carats with 5-digit prices.
The Hope Diamond
The Hope diamond is the most famous blue diamond in the world. GIA graded the 45.52 carat stone as fancy deep greyish blue. The Hope diamond is a rare Type IIb with a unique orange-red phosphorescence.
Blue Diamond Details
Secondary Colors: Common secondary colors in blue diamonds include greenish blue and greyish blue.
Rarity: Natural blue diamonds are exceptionally rare and are priced accordingly.
Grading: Blue diamonds are graded as Faint Blue, Very Light Blue, Light Blue, Fancy Light Blue, Fancy Blue, Fancy Intense Blue, Fancy Dark Blue, Fancy Deep Blue, and Fancy Vivid Blue.
31.06 carat “Wittelsbach-Graff” diamond
This information is taken from http://www.pricescope.com/wiki/fancy-color-diamonds/blue-diamonds