Whats the Deal with coloured stone grading ?

[treasurehunter]

I can grade diamonds but when it comes to these websites that have ''grades' for their coloured stones I have no idea how they graded them as such , all the rubies I have seen whether eye clean or not have been at least I1 to I2 clarity if it were a diamond , yet they are graded as VS

 

[cm366]

In some cases, those grades are the vendor's opinion alone - in others, they may represent the opinion of a lab, if a report has been issued for the stone. Give this a read, might help clarify things a bit....

http://www.ajsgem.com/articles/clarity-grading-colored-gems.html

 

[chrono]

There is no standardized clarity grading, the same way that an IGI SI1 is equivalent to a GIA I3 for diamonds. When it comes to a vendor issued grading, it is even more subjective. I've seen cases where a sapphire is deemed almost flawless but I can spot the inclusions with the naked eye easily.

When it comes to rubies though, because they are rarely clean, GIA has a different standard for them. These are pretty much the same thing the link CM provided:
http://www.gemfix.com/GIA_clarity_system.html (GF lists theirs as may be noticeable)
http://www.multicolour.com/catalogue/columns/column01003.html (MC lists theirs as minor eye visible inclusions)
http://www.simplysapphires.com/grading (SS lists their VS as noticeable to obvious)

Ruby falls under a Type II gem, hence a VS stone might have eye visible inclusions. When it comes to coloured stones, throw out the clarity grading and look at the gem itself. If it is eye clean to you, then it passes YOUR eye clean standards.

 

[minousbijoux]

Ruby falls under a Type II gem, hence a VS stone might have eye visible inclusions. When it comes to coloured stones, throw out the clarity grading and look at the gem itself. If it is eye clean to you, then it passes YOUR eye clean standards.

+1, unfortunately. Wish it were easier.

 

[T L]

Unfortunately, colored gems pose a much more complex issue for gemstone grading than your average white diamond.

Many vendors therefore come up with their own homemade system of grading, and for me, that is a conflict of interest, although some are very honest about what they see. However, what they see may differ highly from you may see.

Even the old GIA gemset notations do not have sufficient shades/colors to run the gamut of color/saturation/tone in a gem.

My preference is the AGL color/clarity grading system, but not everyone can afford a high end prestige report for a gem.

Therefore, much of what a colored gem collector knows is based on careful observation of many gem throughout their collecting experiences. However, if you want a great tsavorite, emerald, ruby, sapphire, alexandrite, spinel, etc. . for example, my advice is to look at lots of that particular gem in person, and in various lighting situations. Go to a gem show, view many, and get a good idea of what you like, and what clarity you can tolerate, for your budget. Treatment is also a whole other ball of wax and complicates gem collecting further, but reputable lab reports are very important for any expensive piece.