The Four C’s:
All four of these are important for assessing the value of a diamond. The first three are useful for determining the quality, and will be the main details on a Diamond Grading Report from any gem lab. The last (carat weight), is used to determine rarity and therefore value, as in an Appraisal.
There are also many other important factors to consider, and if you use only these first Four C’s, you will likely be misled. Please consult my tutorials to make sure you avoid the hype and scams.