Diamond Education
Carat
"The weight or size of a diamond is measured in carats (ct.). One carat weighs 1/5 of a gram and is divided into 100 points, so a diamond weighing 1.07carat is referred to as "one carat and seven points."

For Example
0.75 carat = 75 points.
1/2 carat = 50 points.
1/4 carat = 25 points.

When diamonds are mined, large gems are discovered much less frequently than small ones, which make large diamonds much more valuable.

Diamond prices rise exponentially with carat weight. So, a 2-carat diamond of a given quality is always worth more than two 1-carat diamonds of the same quality.

Color
Most diamonds of gem quality used in jewelry vary in shade from completely colorless down to a visible yellow or brown tint.

The rarest and most expensive are diamonds in the colorless range graded D,E and F on a scale that descends to Z. Diamonds with more color than Z, or in other shades such as orange, pink, blue, etc. are classified as "Fancy Colored Diamonds"

Clarity

Since diamonds form under extreme heat and pressure, internal and external characteristics are common. These characteristics help gemologists separate natural diamonds from synthetics and simulants, and identify individual stones. clarity characteristics marked in red for internal, and green for external features; they are useful for identification.
I.F. : Internally Flawless
Free of inclusions. Only insignificant blemishes visible under 10x magnification.
VVS1 - VVS2 : Very Very Slightly Included
Minute inclusions that are very difficult to locate under 10x magnification.
VS1 - VS2 : Very Slightly Included
Minute inclusions that are difficult to somewhat easy to see under 10x magnification.
SI1 - SI2 : Slightly Included
Noticeable inclusions that are easy to see under 10x magnification.
I1 - I2 - I3 : Included
Inclusions that are obvious to a trained grader under 10x magnification and can be easily seen face-up with the unaided eye.
Cut
While nature determined the color and clarity of a natural diamond, man is responsible for the cut quality which brings it to life.

The planning, proportions, cutting precision and details of finish determine how brilliant, dispersive and scintillating the diamond will be. If the cutting factors under man's control are not optimized, the appearance of the diamond can be adversely affected.

Diamond faceting has changed over time, particularly as lighting has evolved. There are many shapes and cutting styles, each with different visual properties. The most popular diamond in the age of modern electric lighting is the Round Brilliant.