First, if you question whether it is real, take it to a jeweler and let them investigate it. Often the diamond will come with a certificate of authenticity. What they look at are as follows: Diamond Color: The degree to which a diamond is colorless..the paler the better Diamond Clarity: Presence of inclusions in a diamond..how clear it is Diamond Carat: Weight of a diamond...size Diamond Cut: Angles and proportions of a diamond...shape All this equates to value of the diamond, but they can tell you whether you have a Cubic Zirconia or a diamond using these values.