“I can’t even concentrate, I called my friends to come over and try it on,” Katie Holmes (in a Balenciaga dress and Tiffany & Co. jewels) gushed to InStyle.com about the 27-carat emerald cut blue sapphire weighing down her right ring finger at the Solomon R. Guggenheim Museum in New York City last night. If diamonds are a girl’s best friend, then the stars were in good company all evening. Fashion luminaries and Hollywood’s hottest actresses came out to commemorate Tiffany & Co.’s presentation of its 2014 Blue Book, which features the brand’s most spectacular jewels.

See More Photos: Celebrities Wearing Tiffany & Co.

Jessica Biel (in an Oscar de la Renta gown and TIffany & Co. jewels) revealed her favorite piece of Tiffany & Co. jewelry. “Diamond and turquoise earrings,” she says. “But my first Tiffany item was one of the thick silver chain-link pieces, I still have it somewhere.” Kate Bosworth (in a Katie Ermilio gown and Tiffany & Co. jewels) also showed up at the event, and was joined by husband Michael Polish. The most important Tiffany & Co. piece in her life? “My husband’s wedding band,” Bosworth says.

In addition to showcasing the luxury brand’s rare diamonds and precious gemstones, the soirée also featured a special one-night custom projection of “The Diamond Sky,” a mapping installation by the Leo Kuelbs Collection, which was appropriately inspired by the Tiffany diamonds and new book. Other guests in attendance included Seth Meyers with wife Alexi Ashe, Nora Zehetner, Lindsay Ellingson, and Hilary Rhoda.

Click through our gallery to see photos of more celebrities at this week’s hottest parties!