Cut: This includes the various proportions, angles, symmetrical facets, brilliance, fire, scintillation, and polish of a diamond. All of these will determine if and how much the diamond can sparkle and the overall look and feel of the diamond. A proper cut grade is necessary for a diamond to be brought to life. The angle in which light strikes the facet will impact whether most of the light reflects or refracts. 

Colour: A chemically pure and structurally perfect diamond is perfectly transparent with no hue, or color though, in reality almost no gem-sized natural diamonds are absolutely perfect. The colour of a diamond may be affected by chemical impurities and/or structural defects in the crystal lattice.

Clarity: This is the extent to which imperfections in the diamond exist. All diamonds have certain irregularities and imperfections occuring during formation given they are formed under extreme pressure and heat within the earth. 

Carat : The greater the size of the diamond, the rarer it is. Less than 1 in a million rough stones mined are of sufficient size to result in a complete 1 kt diamond. So all things being equal, the heavier the diamond, the higher price it’ll demand.