Blackened BeautiesThe popularity of oxidized fine fashion jewelry is starting to spill over into bridal cases, now that a few manufacturers have debuted styles with blackened accents. Take Frederic Sage, the Great Neck, N.Y.–based firm, which began testing three blackened styles last year.“We haven’t pushed oxidized styles, but some customers fall in love with them,” says senior vice president Brian Sage, adding that people are drawn to oxidized metals for the way they give black diamonds an even darker edge, or make colorless rocks stand out.Los Angeles–based designer Nancy Newberg has noticed that her line, which includes numerous pieces featuring oxidized surfaces, appeals to customers who like stacking rings. “I sell quite a few oxidized rings to flank existing bands and update traditional sets—especially if a client already has a platinum or a yellow gold ring, the oxi