Cut

Cut indicates the angles and proportions of the diamonds.

A well-cut diamond will present the most brilliance and fire. The proportions between depth and the table of a well-cut stone will create this beautiful reflection.

Diamonds that are cut too deep or too shallow will lose the light from the side or the bottom and will result in losing the brilliance and the value of the stone.

The round diamond is the cut that has perfect symmetry and therefore has the most brilliance from all fancy shapes (Princess, Emerald, Pear, etc...)

Clarity

Clarity will be indicated on the certificate and will refer to the amount of inclusions or imperfections that are in the diamond.

The Flawless and Internally Flawless (completely clean) diamonds are the most rare to come by and therefore are the most expensive ones.

The average consumer will buy VS1 - SI2 clarity that are the most common and got the best value. A magnifying loupe 10x is used in the industry to look at the stones and examine the inclusions. A microscope is being used by the GIA to determine the exact location of the inclusion that is being presented on the GIA chart.

Color

The color of the diamond will be indicated on the certificate, the best color which has the most whiteness is the D color. It's also the most expensive because of its rarity.

The diamond color scale will indicate the differences between the colors.
D - F (The colorless diamonds) are the most expensive and rarely come by.
G - J are the most common colors around the average buyers.
K - M when you start to notice faint yellow tinge.
L - Z when you notice yellow tinges.

Carat

The weight of a diamond is measured in carats and will be indicated on the certificate. Large diamonds are more rarely to be found and therefore their value is higher than small diamonds. 1 carat is equivalent to 200mg and can also be equivalent to a 100 points. Therefore, 50 points will be the same as 0.5 carats.