De Beers' sightholders are a group of 78 cutting and polishing companies worldwide that have first "sight" — or option to buy — of De Beers' rough diamonds. The sights take place 10 times a year, and before each event, these clients put in requests for specific types of diamonds.

Last month, the company cut its rough diamond offer to sightholders by 50 percent, and is likely to do the same for sight appointments this month and March and April, a DTC spokeswoman said, adding that the surplus was the result of weakened demand from the sightholders. "The last two sights of 2008 were smaller than usual, and this trend continued into the January sight," she said.

Sales on the day after Thanksgiving rose to $10.6 billion, according to preliminary figures released Saturday by ShopperTrak RCT Corp., a Chicago-based research firm that tracks sales at more than 50,000 retail outlets.

Last year, shoppers spent about $10.3 billion on the day after Thanksgiving, dubbed Black Friday because it was historically the sales-packed day when retailers would become profitable for the year.

While it isn't a predictor of overall holiday season sales, Black Friday is an important barometer of people's willingness to spend during the holidays. Last year, it was the biggest sales generator of the season.

But experts caution that this year's sales growth may be hard to sustain for the remainder of the holiday shopping season, which has 27 days between Thanksgiving and Christmas instead of the 32 last year. Still, the sales boost was surprising in light of data showing shoppers are scaling back on discretionary spending because of a recession fueled by uncertainty related to turmoil in the world's financial and credit markets.