You will note that I do not use or agree with GIA's grading system and probably many other commercial grading systems in the commercial market. In my opinion a flaw is a flaw and should be graded as such. A flawless gemstone can and does occur in any material and type.

Any type of gemstone that meets the flawless grading criteria below should be graded as a flawless gemstone in my opinion. I do not believe in creating "types" of gemstone catagories and adjusting the grading scale to fit what is most common or what some trade group(s) want to sell in those catagories.

Color is an arbitrary thing and people as well as countries all have different tastes, so there can be a fair amount of variance. In my opinion once the clarity of the stone is graded correctly, then people will decide what color(s) they prefer and make their choices accordingly. Yes, some colors are considered more valuable than others, and in general the more intense and bright the color of a gemstone the more valuable. But I personally feel that the best way to account for color ranges is in the pricing, not grading, because tastes and color perceptions vary so widely.

Tone - This is a method to help describe the tone/saturation of color of a gemstone. This does not describe color, only the saturation of the color.

Pale - almost colorless to 15% tone
Light - 15% tone to 30%
Light/Medium - 30% tone to 45%
Medium - 45% tone to 65%
Medium/Dark - 65% tone to 85%
Dark - 85% tone to 100%

Clarity
IF (internally Flawless) = Free of inclusions under a 10x loupe magnification.
VVS1 (very, very small inclusion) = Very small inclusion(s) under 10x loupe magnification, difficult to find.
VVS2 (very, very small inclusions) = A few, very small inclusions under 10x loupe magnification, difficult to find.
VS1 (very small inclusions) = Very few small inclusions recognizable by an expert under 10x loupe magnification.
VS2 (very small inclusions) = Some small inclusions recognizable by an expert under 10x loupe magnification.
SI (small inclusions) = Several small inclusions easily recognizable under 10x loupe magnification, but not diminishing the brilliance appreciably. This is what I would call "eye clean" but this term is often abused.
I (inclusion) = Inclusion(s) easily recognizable under 10x loupe magnification, but not diminishing the brilliance appreciably.
P1 (1st Pique) = Inclusions at once recognizable under 10x loupe magnification, but not diminishing the brilliance of the stone appreciably.
P2 (2nd Pique) = Larger and/or many inclusions, slightly diminishing the brilliance, recognizable with the naked eye.
P3 (3rd Pique) = Large and/or many inclusions diminishing the brilliance, easily recognizable with the naked eye.

None Known - No known treatments, please note that there could be a very small possibility of some treatment done that the cutter maybe unaware of at the mine or before the cutter aquired the rough/stone. In general there will be no treatments of any kind in this catagory.
Unknown, but likely heated - No known treatments, but this type of rough/stone is often heated.
Heat - Heat only. Heating is a fairly common practice and it is done to lighten or eliminate an unwanted color in some rough/cut stones.
Unknown, but likely treated - No known treatments, but this type of rough/stone is often treated.
Treatment(s) - Treatment(s) are a fairly common practice and there are various types of treatments, whatever the treatment is will be listed and defined.
Irradiated - Irradiation is used to change or improve the color of a cut/rough stone.
Uknown - I have no idea if any treatments have been done.

If you have any questions, please inquire.