UPDATE 9/8/2011: The "Golden Eye" diamond fetched a final bid price of $2,843,623 which met the reserve.

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Two spectacular yellow diamonds are set to sparkle at auctions this fall. One fits the best in class category, the other has a sordid past.

First is a rare "vivid fancy" pear-shaped gem of 32.77 carats, expected to fetch up to $8 million at a Christie's auction in New York on Oct 18. The second is an "internally flawless" 43.51-carat stone — known as the "Golden Eye" — that is now part of a government seizure auction online through Thursday.

Investors, especially in Asia, are increasingly turning to diamonds as a hard (and shiny) asset other than gold. According to a Financial Times article last week, the value of top quality polished diamonds of 5 carats have risen to about $150,000 a carat, up from about $100,000-$120,000 a year ago.

Unless a gem bubble lurks, the prospects are good that these beauties will be bid to high amounts based on current market demand and the so-called four Cs of diamond grading: cut, clarity, color, and carat weight.

The piece to beat may be The Golden Drop, a pear-shaped yellow diamond of 18.49 carats, that achieved a per-carat price of $203,000 when it sold in June 1990 at Christie’s London.

Christie's offering this October is an extraordinarily vivid yellow diamond, blessed with a far deeper hue than the common yellow, and ranked by the Gemological Institute of America (GIA) as one of the rarest and most highly saturated colored stones in its class.

Only about one in 10 million diamonds possesses a color pure enough to qualify as fancy vivid.

Rahul Kadakia, Christie’s Head of Jewelry for Christie’s Americas, explained, “In the world of diamonds, a naturally colored stone of this incredible color and size represents a freak occurrence -- an extremely rare geological phenomenon."

Of a less satuarated yellow, the "fancy intense" diamond seized by the government came from an Ohio businessman who was convicted of money laundering and conspiracy. Prosecutors said he tried to sell the diamond and an estate once owned by boxer Mike Tyson to an undercover FBI agent, for $19.5 million and a boat, according to the AP.

Maryland-based Bid4Assets is auctioning the "Golden Eye" diamond for the U.S. Marshals Service. Bidding went to $1.52 million by Tuesday evening and ends on Thursday.