The true beauty of a diamond lies in its ability to reflect light. A diamond, not cut to correct proportions, will appear dull and lifeless. The basic elements in which the quality of a Diamond is expressed have been publicized and popularized as the 4 C's. Carat, Cut, Quality and Colour make up the elements. Proportions (Height and width ratios) Symmetry (Placement and size of facets) and Polish( the surface of facets) should all be considered before you make a decision. Also, insist on a laboratory certificate that will confirm the characteristics.