Diamond Chic

Classic elegance or big bling? As Valentine's Day approaches the gift of diamonds is not only your girl's best friend, but can make you a close second. Choosing what to buy in a climate where diamonds are bedecking everything from ladies' décolletage to outsized gaudery, while changing colors and cuts at will, can be daunting, though. Here's how today's diamonds are reconciling timeless sophistication with cutting-edge style.

You doubtless know the four "C"s of diamond buying: carat, clarity, color and cut. Careful buyers consider a little-known, but equally as important, fifth "C": certification. A certificate from an independent laboratory such as the Gemological Institute of America assesses gem quality, provides identification in case of theft and guarantees authenticity. Polar Ice Canadian Diamonds (www.polaricediamonds.com) puts its own mark on the fifth "C." The company's Canadian—government—certified diamonds are laser-engraved with an identification number and then tracked from the mine through the cutting and polishing processes to you. The certificate lists your diamond's unique attributes and exact origin—you can even request the name of the craftsman who cut it. Better yet, take your gal to the gem-rich Northwest Territories for an Arctic diamond tour and let her choose her own piece of ice.

If you don't have the wanderlust to brave even a jewelry store, visit www.BlueNile.com, the largest online diamond retailer. Blue Nile woos its customers with excellent service and some of the best prices on- or off-line by acquiring its gems (some of which are pictured here) early in the supply chain. "Instead of buying a one-carat diamond elsewhere, our customers find that they can purchase a 1.5-carat stone from us for the same price," explains Blue Nile diamond and jewelry expert John Baird. Opt for its hand-selected Signature Diamonds, which are among the top 1 percent of diamonds found in the world.

Remember, styles change. It used to be the most-prized diamonds were colorless (i.e., not yellow). Now the extraordinarily rare (and expensive) pink or blue diamonds are in fashion among the chicest sets.

If you prefer to remain true to the classic white, then play with the plethora of cut options. The round brilliant, which maximizes a diamond's natural sparkle, is the perennial favorite, while vintage cuts, especially the square Asscher, are back in vogue. The up-and-coming darling, however, is the cushion cut, a square cut with angled corners. Want to take it to the next level? Tuck a cushion-cut diamond between two baguettes and watch her go wild.

Still not convinced? Victoria's Secret, the boudoir outfitter, recently unveiled its Fantasy Bra featuring a 101-carat flawless pear-shape diamond. Lingerie and diamonds: consider it a gift that you both can appreciate (www.victoriassecret.com).