Diamond proportion is very important. Round brilliant diamonds are usually cut with 58 facets. The proportionional similarity of these facets on the diamond affect how much light will be reflected to the viewer. The better the cut, the more the diamond will sparkle. Ask for the table percentage. A good table percentage is between 55-60%.
How does pavilion depth affect a diamond's cut?
Precise artistry and workmanship are required to fashion a stone so its proportions, symmetry and polish deliver the magnificent return of light only possible in a diamond.
A pavilion depth that’s too shallow or too deep will allow light to escape from the side of the stone or leak out of the bottom. A well-cut diamond will direct more light through the crown, creating maximum brilliance.
Carat is the measurement of a gem's weight. Larger gems often cost more per carat because of their size. There are 100 points to a carat. A 50 point diamond equals 1/2 a carat. One gram is 5 carats. Ascertain the actual point size of a diamond instead of the fractional weight. Some jewelers will try to sell a .90 diamond as a 1 carat diamond which would be much more expensive.
Clarity or clearness ranges from flawless (perfect) to I (included):
Colors range from D - X for white and yellow diamonds. D is the whitest. At S they are "Fancy" yellow Diamonds. There are also, pink, red, green, blue and brown diamonds which are typically irradiated.