A Persian carpet decorated with swirling vines and vibrant flowers that was stored for decades by the Corcoran Gallery of Art sold Wednesday for more than $30 million. That sum, fetched at a Sotheby’s sale, shattered the previous record for rugs sold at auction. But it won’t help the struggling Washington gallery overcome its financial woes because the money must be used for future acquisitions, not to help the bottom line.

The winning bid for the Clark Sickle-Leaf Carpet stunned viewers and participants at the sale, in which 25 rugs and carpets were auctioned off to raise money for new acquisitions of American and contemporary art at the Corcoran Gallery. The anonymous bidder, who participated by phone, paid $33,765,000 for the 17th-century Persian piece, which came from the bequest of William Clark, the industrialist and U.S. senator who donated more than 200 works of fine art and rugs to the Corcoran upon his death in 1925. Before Wednesday’s sale, a blue leaf-patterned 17th-century rug from southeast Iran held the global record, selling for $9.6 million at Christie’s in London in 2010.

“I thought it might sell for 10 or 15 million dollars,” said Mary Jo Otsea, the auctioneer and senior consultant for rugs and carpets at Sotheby’s. The auction company estimated the carpet would sell for between $5 million and $7 million. “No one ever expected to see it on the market. Its beauty and rarity — the closest comparables are in museums.”

Which is why, Otsea believes, the carpet sold for such a high figure. Rarity pushes the value of art up, and most Persian carpets are subdued in patterns and hues. But the roughly 8-by-6-foot carpet is said to be the epitome of the “vase” technique, perfected during the Safavid dynasty in Persia. It was last displayed in Washington at the Sackler Gallery in 2003 and the Corcoran Gallery in 2006.

The Sotheby’s sale also comes as the classical carpet market — carpets made during the 16th and 17th centuries — is booming. A decade ago, only the most famous Persian rugs would sell for seven figures at auction. But collectors in Asia and the Middle East are investing in Persian rugs with the same enthusiasm they are showing for rare, valuable contemporary works. Museums in the Middle East are also investing in Islamic art collections, including the Museum of Islamic Art in Doha and the Guggenheim Abu Dhabi, now under construction. And renewed interest in Islamic art in the West has probably contributed to prices, too, with the 2011 opening of the Metropolitan Museum of Art’s New Galleries for the Art of the Arab Lands and last year’s opening of the Department of Islamic Art at the Louvre.

  The Corcoran Gallery of Art’s Clark Sickle-Leaf Carpet, from the collection of William Clark, was sold at auction for $33 million. (Collection of William A. Clark; Courtesy Corcoran Gallery of Art)

As for who bought the record-breaking rug, it’s anybody’s guess. Sotheby’s never talks, and the Corcoran doesn’t know.

“It could have gone to the [Persian] Gulf countries, to Europe or to an institution being built somewhere,” said Peggy Loar, interim director of the Corcoran. “In terms of patrimony, or where these carpets came from, there’s great interest in bringing them home.”