The following grading system for coloured gemstones is used by Rough Creations. It was taken from Dan’s Starr Gems grading system which was based in turn on Jeff Graham’s modified GIA (Gem Institute of America) coloured stone grading system.
IF (internally flawless) = Free of inclusions under a 10x loupe magnification
VVS (very, very small inclusion) = Very small inclusion under 10x loupe magnification, difficult to find.
VVS2 (very, very small inclusions) = A few, very small inclusions under 10x loupe magnification, difficult to find.
VS (very small inclusions) = Very few small inclusions recognisable by an expert under 10x loupe magnification.
VS2 (very small inclusions) = Some small inclusions recognisable by an expert under 10x loupe magnification.
SI (small inclusions) = Several small inclusions easily recognisable 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 recognisable under 10x loupe magnification, but not diminishing the brilliance appreciably.
P1 (1st Pique) = Inclusions at once recognisable 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, recognisable with the naked eye.
P3 (3rd Pique) = Large and/or many inclusions diminishing the brilliance, easily recognisable with the naked eye.
None Known – No known treatments, please note that there could be a very small possibility of some treatment done that I am unaware of at the mine or before I acquired the rough/stone. In general there will be no treatments of any kind in this category.
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. I personally do not find heat an issue, but it should be noted.
Unknown, but likely heated – I do not know of any treatments, but this type of rough/stone is often heated.
Irradiated – Irradiation is used to change or improve the color of a cut/rough stone.
Unknown – I have no idea if any treatments have been done.