Diamonds vary in color from colorless to light yellow.  Diamonds are rated by a color rating system by the GIA (Gemological Institute of America.  The "D" through "J" rated diamonds are the most desirable and most expensive.

A flat angled surface is called a facet.  The placement of the facets on your diamond affect the brilliance and beauty of it.  An improper cut will make the diamond look glassy, but when it is properly cut, the diamond will look brilliant.  The most popular.  Another thing that people get confused is the cut and shape of the diamond.  When you hear "Marquise Diamond", that is talking about the SHAPE.  There are several different shapes:  Brilliant (round), pear, princess, emerald, marquise, oval and heart-shaped.

The weight and size of a diamond is expressed in carats.  One carat has 100 points.  So, when are looking at a ½  (.50) carat, you know it have 50 points.  Both the weight and size will determine the value of the diamond.

Almost all diamonds have some naturally occurring characteristics called inclusions.   If a diamond has no inclusions, it is considered Flawless.  These diamonds are extremely rare and VERY expensive.  The size, the location and the number of inclusions determine the clarity rating. The less inclusions that your diamond has, the more expensive.  If you can see an inclusion with your naked eye, it will be graded in the "I" category.