Not even a mountain of cushion-cut diamonds can soften a blow like this: This winter, after nearly six years of marriage to Revlon chairman Ron Perelman, Ellen Barkin was surprised with divorce papers and watched by security guards as she moved out of the couple's Manhattan townhouse. Since their 1999 courtship, Perelman had given Barkin many significant gems, including her first strand of pearls and a lollipop-size 22.76-carat diamond ring. Now, she told The New York Times, "these are just not memories I want to wear." So the actress, currently shooting Ocean's Thirteen, will auction 120 pieces at Christie's in New York on Oct. 10. The move is not unusual, says François Curiel, chairman of Christie's Europe: "The three engines of our business are Death, Divorce and Debt." Her act of closure is a boon for collectors, as Barkin owned jewels by Bulgari, Cartier, and 17 from JAR, by Joel Rosenthal, who makes only 70 to 80 pieces a year. "These don't come on the market often," says jewelry historian Elyse Karlin. "They will create quite a stir." And quite a profit. The auction is expected to take in $15 million, which Barkin (whose divorce settlement was worth about $20 million) plans to put toward her film production company. Notes Karlin: "It's an interesting way to set yourself free emotionally."

JAR TOPAZ, DIAMOND, AND RUBY EARRINGS
"I was especially in love with those," Barkin says on the Christie's Web site. "I wore them to Oscar parties." Valued at $60,000-$80,000, "these are very rare because there is a touch of red," says Curiel. "Normally topaz is rather brownish and common."

JAR DIAMOND BANGLES
The pavé-set bands boast a faint pink and a colorless cushion-cut diamond; one stone is from Golconda, a now-closed mine in India known for extremely rare gems. (Estimated price: $350,000-$500,000.) Says Barkin of the designer: "He's like the Matisse of our time."

DIAMOND PENDANT NECKLACE
"I wore it every day and night, I slept in it, it never came off," says Barkin of this necklace set with a 16.93-carat briolette diamond, which may sell for up to $800,000. "It was like a wedding band." (Her actual diamond wedding band, from Cartier, is also on the block.)

DIAMOND EARRINGS
"When I wore those, my clothes were always very simple," says Barkin. "That was enough adornment for me." Modeled on a faux stone pair worn by Marilyn Monroe, Barkin's are real diamonds, and will likely go for $150,000-$200,000.

EMERALD EARRINGS
Featuring pearls, emeralds and diamonds, the drop earrings are expected to fetch up to $180,000. "To have a pair of perfectly matched emeralds in color, size, purity and transparency is quite rare," says Christie's U.S. head of jewelry Rahul Kadakia.

JAR PEARL AND DIAMOND EARRINGS
Because the pearls are natural—noncultured pearls are almost nonexistent these days—the pair could sell for up to $500,000.

JAR AQUAMARINE AND MORGANITE EARRINGS
Set within diamond frames, they could sell for $80,000. Designer Joel Rosenthal, says Barkin, "taught me how to wear my jewelry." Wear it she did. "I didn't want to keep it in a vault. I wanted to enjoy it. I wanted to feel the earrings clang on my ears while I was running around town."

VAN CLEEF & ARPELS EMERALD, DIAMOND AND GOLD CUFF
Made in the 1950s, the bracelet has about 30 carats of square-cut emeralds and 25 carats of diamonds; it will likely sell for up to $180,000. The auction, officially titled "Magnificent Jewels from the Collection of Ellen Barkin," also includes belle epoque, art deco and modern pieces.

Expected to earn $15 million, the sale may rank behind only the Duchess of Windsor and Princess Salima Aga Khan jewelry auctions