NEW YORK (AP) _ The biggest and most valuable diamond ever to go on the block was sold Tuesday to an anonymous bidder for a world-record $9.13 million.

The buyer bid by telephone for the 85.91-carat pear-shaped diamond, said Diana Levitt, director of corporate affairs for Sotheby's. The sale was part of a jewelry auction that brought in a total of $36 million.

''The sale was a great success, achieving a record for a jewelry sale in America as well as establishing a record for any piece of jewelry sold at auction,'' said John D. Block, director of Sotheby's jewelry division.

Bidding for the diamond took two minutes and opened at $6 million. The gem itself went for $8.3 million; the remainder of the price is the buyer's premium.

The diamond has been graded D color, meaning it is of the highest possible rating, perfectly cut and flawless.

Neil Letson, gemologist and jewelry historian, said the diamond has been described by a leading connoisseur of gems as a ''drop of frozen light.''

''It represents the very essence of this planet in its simplest and purest form,'' he said.

The old record was set in 1980 by Sotheby's in Geneva, where $6.6 million was bid for a pair of ear pendants with four pear-shaped diamonds totaling 131.86 carats.