Determining Diamond Quality by the 4 C's

Diamond quality is evaluated by four characteristics called the 4 C's. They stand for carat weight, clarity, color and cut and all stones are graded and valued based on these four. Finding a good balance between the 4 C's is the best way to buy a diamond.
Carat Weight : In 1913, a standard for measuring the weight of diamonds and gemstones was created. The standard weight known as a carat, was the same title given to pre-standardization measurements and actually derives from the word for carob seed, which was the unit of measurement by which gemstones were weighed in ancient times. One carat is equal to 1/5 of a gram and is then divided into smaller units of measure, called points, each carat equaling 100 points.

Clarity : The clarity of a diamond is a measurement of the inclusions or blemishes inside and/or on the outside of a diamond, under a 10x microscope. The rating system is subjective to the master diamond cutter, though the guidelines are as follows :

'F' Flawless
No internal or external flaws can be seen under a 10x microscope when viewed by an experienced diamond grader.

'IF' Internally Flawless
No internal flaws may be seen under a 10x microscope by an experienced grader, though there may be a few minor external blemishes.

'VVS1, VVS2' Very Very Slight Inclusions
The diamond will contain inclusions but they will be difficult to see for an even experienced grader under a 10x microscope.

'VS1, VS2' Very Slight Inclusions

'SI1, SI2' Slight Inclusions
The diamond will contain inclusions easy to spot under a 10x microscope and may be visible to the naked eye.

'I1, I2, I3' Included
Inclusions are visible to the naked eye.
Color : Though most people believe that diamonds are colorless, diamonds, in fact, exist in every color of the rainbow. The colored diamonds, known as fancy diamonds, are even more valuable than traditional white diamonds and can be red, pink, blue, green, orange and brilliant yellow, not to be confused with slightly yellow, which is considered to be a poor quality white diamond. White diamonds are graded on a chart and colorless diamonds are considered the highest quality. The quality ranges from colorless (letters D, E and F), to almost colorless/brown/gray (letters G, H, I and J), to faint yellow (letters K, L and M) all the way to the letter Z, which signifies a light yellow diamond. Because colorless diamonds are considered the most prized, diamond quality in the higher letters (D, E, F) are the better choice.

Cut : The fourth “C”, cut plays an important role in diamond quality and is the only “C” on which humans have any control. Cut refers to the geometric shape and proportions to which a diamond is pared. A round cut diamond has 57 or 58 facets. Each facet must be cut and polished to the exact specifications in relation to the other facets on the stone to create the most fire and brilliance. A poorly cut diamond can ruin the value of a stone. If facets do not match exactly, the diamond quality decreases.