RAPAPORT... Round diamonds have long been the most popular in the US, but fancy shapes also have a following in certain cities, according to a study by Blue Nile. Round-cut diamonds continue to be the most popular shape inmost states, accounting for 66% of nationwide orders, the jeweler said lastweek. However, when it comes to fancies, Blue Nile receives the most orders foremerald and princess cuts from Dallas, Texas, while pear-shaped and radiant-cutdiamonds are most popular in New York City. Los Angeles residents are thebiggest consumers of vintage-inspired marquise-cut stones, and Chicago took thetop spot for oval-cut diamonds. Orders for ovals have doublednationwide in the past three years, Blue Nile noted. "While the round cut is always the most popular because ofhow it optimizes fire and brilliance, we've noticed that engagement-ring trendsvary based on where our customers reside, and it's those trends that tell astory of their own," said Blue Nile chief merchandising officer KatieZimmerman. Solitaires have been the preferred setting for decades, accounting for 39% of all orders, while halo settings came in second. The biggest stone Blue Nile has sold in the past year was an8.04-carat princess cut, which was purchased in Charleston, South Carolina. Honolulu, Hawaii, is home to the largest heart-shaped diamond purchased,weighing 4 carats. When it comes to metals, platinum is the top choice nationwide, comprising 42% of total US sales, with San Francisco residents making the majority of purchases. Atlanta,Georgia, orders the most rose gold, and sales of the metal in the country havedoubled in the last three years, the jeweler said. Gold is most popular inTexas, with Dallas ordering more white gold than any other city, while Houston optsfor yellow. Image: A platinum-set round solitaire engagement ring. (Blue Nile)