The Four Cs -
First,
To determine a diamond's value, experts use the Four Cs—cut, color, clarity, and carat weight.
Cut -
When people think of cut, they often think it’s the shape of the diamond. But, it’s about how light is returned due to a diamond’s facets. Cut is responsible for brilliance, fire, and scintillation of a diamond.
Color -
A diamond’s color is measured using the GIA® D-to-Z diamond color grading system. This system is the most widely accepted for grading. All diamonds are evaluated based on the absence of color.
Clarity -
Just as a diamond’s color is graded on the absence of color, the diamond’s clarity is graded on the absence of inclusions and blemishes.
Internal characteristics = Inclusions
External characteristics = blemishes
Carat -
In addition to color, cut, and clarity, carat weight directly correlates to price of the diamond. This happens because the supply is low (larger = rarer) and demand is high (larger = more popular).
Next, Shape.
Now, Lab-Grown or Natural Diamond.
What's the difference?
Lab grown diamonds are a real diamond at an attractive price. They are becoming more and more popular. When you put a lab grown diamond next to a naturally grown diamond you can not tell the difference. Lab grown diamonds have the same physical, chemical, and optical properties as a natural diamond. The only difference is the origin which takes a highly specialized piece of equipment to test it.