The Gemological Institute of America (GIA) ranks diamond cuts from Class I (ideal) to Class IV (poor). These rankings should serve as only a guide: Ask to see a range of cuts and use your eye to examine each. Stay away from stones with a dull or dark center — your diamond should have symmetrical facets and twinkle with a rainbow of colors.

Simply put — and all other things being equal — the less color a diamond has, the more valuable it is.

But unless you’re a trained jeweler, you’re not likely to spot the difference between a colorless diamond (which is, in fact, extremely rare) and a nearly colorless diamond, once it’s mounted in a setting.