Dear Rubymu -
I looked it up and here's what I found:
GIA Make Classes
CLASS 1 2 3* 4**
TABLE 53-60%*** 61 - 64% 65 - 70% +70%
CROWN 34-35° 32 - 34° 30 - 32° -30°
GIRDLE medium to slightly thick thin to thick very thin to very thick extremely thin to extremely thick
PAVILION 43% 42 - 44% 41 - 46% -41 / +46%
CULET none to medium slightly large large very large
FINISH very good to excellent good fair poor
* Class 3 also includes stones with 51 or 52% tables or 37 crown angles.
**Class 4 also includes stones with tables less than 51%, crown angles more than 37 , or major symmetry variations.
***Table size for Class 1 goes up to 61 to 62% in stones under 0.50 ct.
_____________________________________________________________________________________
Class 1: The cutting precision of what we might call Class 1 stones strikes the trained eye immediately. The impression is one of a harmonious balance between both the various physical dimensions and components of optical display -brilliance, fire, and scintillation. Stones in this class required extra time and care to produce a high-quality finish, so they normally cost more.Generally, in sizes from about 0.50 carat up to be considered Class 1, stones must have table sizes from 53 to 60 percent, crown angles from 34° to 35° , even girdles that are medium to slightly thick, pavilion depths very close to 43 percent, small to medium culets(or undamaged), and very good to excellent polish and symmetry. In smaller sizes, slightly larger tables - up to about 62 percent - are acceptable, but the other criteria are the same.
Class 2: These stones are very attractive, with minor variations which few customers and trained or experienced jewelers would recognize. These stones have table sizes from 61 to 64 percent, crown angles from 32° to 36° , thin or thick girdles, pavilion depths from 42 to 44 percent, small to slightly large culets, and good polish and symmetry.
Class 3: Many of these stones have been stretched to push them into higher weight categories. An example of stretching would be a large table and shallow crown that were cut to obtain a stone weighing a little over one carat.
Class 3 stones have table sizes from 65 to 70 percent, crown angles from 30° to 32° , very thin or very thick girdles, pavilion depths from 41 to 46 percent, large culets, and fair polish and symmetry.
Class 4: Class 4 stones have such variations that even the untrained observers sense that something is amiss, even if they can not say exactly what it is.Class 4 are stones with table sizes larger than 70 percent, crown angles shallower than 30° , extremely thin or extremely thick girdles, pavilion depths shallower than 41 percent or deeper than 46 percent, very large culets, poor finish, and major symmetry variations.
