Diamonds might be a girl's best friend, but they're also as common as a flat highway in East Texas. The mall's no help. Every bauble there is a cookie-cutter version of every other. Instead, try A.A. Benjamin, a tiny showroom hidden in the back of a bank building. Among the many antique and estate delights laid out in the glass cases are hand-cut, one-of-a-kind diamonds, rubies, emeralds and sapphires set in platinum and gold dating back to the 1800s (some even further). Cartier, Van Cleef & Arpels and La Cloche are just a few of the designers represented in their collection. If they don't have what you want on hand, they'll go looking for it. And if you're really special, they'll even bring the merchandise to you, to view in the comfort of your office or home. You can't get more uncommon than that.