5 incredible facts about this $31.8m rare blue rock

Dubbed the De Beers Millennium Jewel 4, the stone is what diamond expert Tobias Kormind of 77 Diamonds describes as a "once in a lifetime" market shift in the industry, where auctions of blue diamonds are breaking records, one after the other.

The 10.10 carat rock went under the hammer Tuesday at Sotheby's in Hong Kong, but has already clinched the title of largest Oval Fancy Vivid blue diamond to appear at auction.

Having sold at $31.8 million it has broken the record for most expensive diamond sold in Asia. Here are five things you might not know about this diamond.

1. It was part of the biggest diamond heist in history... almost

This stone was first unveiled in London in 2000 as part of the Millenium Jewels exhibition, where it caught the attention of a local gang of robbers.

An attempted robbery ensued, which was foiled by the Metropolitan Police.

If the robbery had been successful, the thieves would have made off with $300 million worth of stones in total, which would have made it the biggest diamond heist in history.

"The attempted heist was incredibly professional," says Kormind. "The robbers had figured out how to weaken the protective glass and had an escape route planned along the river. They likely would have gotten away with it if the Metropolitan Police were not given an anonymous tip, which allowed them to prepare for the heist in advance."

2. The industry is 'obsessed' with blue diamonds

In November last year, a 12.03 carat fancy vivid blue diamond named Blue Moon sold for a whopping $48.4 million, making it the most expensive diamond to have ever sold at an auction.

According to Kormind, this record-breaking sale kick-started an industry-wide obsession with blue diamonds, pushing collectors to release more of these blue stones to the auction market than ever.

A diamond belonging to actress Shirley Temple will auction later this month, and the Oppenheimer Blue (a 14.62 carat stone that will be the largest Vivid Blue diamond to ever appear at auction) will go under the hammer in May.

"The majority of these stones are traded on the private market and previously only a handful had ever come to auction. What we're witnessing is a once in a lifetime series of events -- I don't think we'll ever see a moment in time like this again."

3. It's pricey because of its color

Fancy colored diamonds are already rare, but some colors are more desirable than others.

"Red is the rarest diamond color as there are only around 100 known recorded red diamonds in the world. Blue comes in as a close second," Kormind explains.

"Yellow diamonds also hold tremendous value, but a few years ago, several mines with yellow diamonds were discovered and their rarity was reduced. The yellow diamond never quite recovered. Brown and gray diamonds are the most common, and therefore least valuable on the spectrum."

4. Auctioneers have been careful not to 'burn' this stone

The value of a rock can be increased or decreased depending on its treatment and reception during an auction.

A stone that is "too known," says Kormind, can develop a tarnished reputation and a stigma that it is unwanted.

"A desperation to sell a diamond decreases its value. If it's being pushed too hard and is still not well received, we call this 'burning the stone.' People begin to wonder, 'What's wrong with it?' and 'Why hasn't it sold?'"

5. 'Vivid' and 'Fancy' are more than just adjectives

The De Beers Millennium Jewel 4 is described as a "Fancy Vivid blue" diamond, but these are more than just adjectives -- the terminology is used as part of a color grading system that alerts diamond experts of the tremendous value of this rock.

Read: Prehistoric beasts turned to tiny beaded jewels

"It allows us to differentiate the value of one blue diamond from another," says Kormind. "The range extends from Light blue, to Fancy Light blue, to Fancy Intense blue and so on."

"A Fancy Vivid blue is particularly special, it describes the highest possible color rating for this diamond."

(CNN)