It's accepted wisdom that cut is as important to a stone's appearance as the other three Cs—sometimes more so. Yet there is no universally accepted system for grading cut and no grade at all from the biggest lab, The Gemological Institute of America's Gem Trade Laboratory. That may change. After a decade of research, GIA is coming forward with a cut grade—or something that might be a cut grade, depending on what the trade thinks. With characteristic caution, it's not committing to anything more than putting the grade on reports next spring—a plan that GIA has announced, and not followed through on, before. If it does happen, it will be the lab's biggest change since it began issuing reports in 1955, and it could, like the GIA scales for color and clarity, give the trade a new "language" and way to look at diamonds—all of which increases the pressure on GIA to get it right.