Carat and Clarity
The Four C's are the traditional guidelines used to assess the quality of a stone. A carat is approximately one fifth of a gram. The size and location of inclusions -flaws- in a diamond determine its clarity and ratings. The amount of clarity ranges from flawless to most desirable, to imperfect. The fewer the inclusions the greater the quality and the value.
Cut and Color
A diamond's cut determines its brilliance; more facets, or surfaces, mean more sparkle. Color is determined an a scale from D- the highest - to Z - the lowest. The whiter the stone the closer it is to a D rating. Subtle traces of a color such as brown, yellow or gray are not desirable. Which are colored and extremely rare.