The centerpiece of Christie's October 18 jewelry sale in New York will be a miraculous 32.77 carat yellow diamond, ranked by the Gemological Institute of America (GIA) as one of the rarest stones in its class. The sale was announced last week, just two days before the Financial Times reported that diamonds are the new alternative investment of choice, especially in the Asian market.

The pre-sale estimate for the mammoth gem is $6-8 million. According to a spokesperson for Christie's, the stone will be soldunmounted so that the new owner can choose how it will be worn — as aring, pendant, or tiara. 

The stone is pear-shaped and brilliantly cut. It's grade is "fancy vivid" — meaning it has a deep yellow hue — with a very good polish and symmetry. Colored diamonds are quite rare, as the color comes from an impurity in the chemistry of the diamond, generally a very stable material. Of all the colors that diamonds can be, the yellow (caused by nitrogen impurities) is the most common. However, most yellow diamonds are quite pale. The extraordinary vividness of the Christie's gem makes this particular diamond extremely rare, according to the GIA.

The price of diamonds has shot through the roof in the last two years, and the average price per carat of top-quality, polished five-carat diamonds is up to $150,000 from $100,000-120,000 just a year ago, according to the FT. Between the rare qualities of the yellow diamond and the confidence in the market for gems, bidding on this particular lot could get crazy. Alternatively, if the diamond fails to live up to the pre-sale estimate, it could signify a deflation of a gem bubble.

One possible bidder to look out for is London-based jewelry dealer Laurence Graff, who has set the previous two records for highest-price ever paid for a diamond, first for $24 million for the 35.56-carat "Wittelsbach Diamond" and then in November 2010, with his $46 million purchase of a 24.78-carat fancy pink emerald-cut diamond at Sotheby's in Geneva, which he then christened the "Graff Pink."