Why is this?

[MAC-W]

I’ve been following the thread on RockyTalk about Trade Participation and a large part of that thread has degenerated into to discussion about reflector technology and whether its good (oh yes it is! oh no it isn’t! Oh yes it is! etc etc) and whether all diamonds should be sold with these tools & reports

But it got me thinking.............. why is reflector technology and cut grade technology (ASET, Idealscope, ISEE2 etc) which is so passionately required and defended on RockyTalk, never mentioned on the coloured stones forum? None of the coloured Stones vendors, (even what I would term the “premium” ones), seem to have anything about these tools.

Are they only applicable to diamonds ?

I hear a lot on here that coloured gemstones are cut predominantly for colour – does that mean these tools and technologies are really only good for sparkle and not really practical for maximizing colour?

But it seems to me some of these tools could be useful for some aspects of coloured stones as well eg, leakage. Have I got it wrong?

Can someone please help clarify this for me?

And explain why these tools are never mentioned with regard to coloured stones?

 

[Allison D.]

MAC, it's because the priority in the world of colored stones is not always cut and those tools only offer insight into cut.

In fact, most often, it's tone and saturation of the color and how closely the stone comes to the prescribed optimum.

Keep in mind, too, that colored stones come in different varieties, so they often have different refractive index properties.

 

[LD]

None of those pieces of equipment test colour! In coloured gemstone world, colour is KING! That comes first and foremost!

 

[Michael_E]

But it seems to me some of these tools could be useful for some aspects of coloured stones as well eg, leakage. Have I got it wrong?

Can someone please help clarify this for me?

And explain why these tools are never mentioned with regard to coloured stones?

Sure, I think that I can help. The Idealscope and the ASET tool are both designed with the refractive index of diamond in mind and have a built in bias for particular cut styles. The refractive indices of colored stones all vary depending upon the stone type and so those tools would have limited use in analyzing the cut of colored stones. Colored stones also have widely varying intensities of attenuation, (the amount that light is absorbed in it's travel through each millimeter of stone), of light based on things like how deep the color is and what axis the light is traveling on. This complicates matters so much that the use of diamond based tools would be of little use in determining if a colored stone is cut well or not. You know what really works well? Looking, in person, at the cut stone in all kinds of different light. There are a number of tools that can help in predicting what a stone will look like once it's cut, but these are not always right and can not be used to tell if a stone is well cut after it's been cut.

You need to remember that all those diamond tools are designed to tell you whether a stone is well cut before it gets to your hand and they are generally weighted to tell you something about how bright a stone may be. Since they are unconcerned about color, they can't address things like color zoning and location, depth of color, light path length and patterning that is designed to be unique. I doubt if there will ever be any tools, other than a camera, that can give you much of an indication beforehand about how well a colored stone is cut. I also doubt that anyone would be crazy enough to try to formulate some idea of what constitutes beauty in a colored stone since there are as many variables as there are viewers. It's kind of funny since it turns the arguments about colored stones into arguments about pictures and we all know how accurate that is.

 

[MAC-W]

Ah, I hadnt really thought about things like the different refractive indexes and attenuation.

It makes sense now - Thank you so much for the explanations.

 

[chrono]

The goal/aim of colourless diamonds only partially intersects with the goal/aim of coloured gemstones. Since colourless diamonds have no colour, there is nothing else going for it except light performance. Hence, cut becomes of utmost importance. Those tools have been designed to check for light performance and cutting symmetry.

Coloured gemstones are called as such because colour is the top priority. Prices are set according to the colour, first and foremost, with the other Cs below it. Perhaps a couple tools might come in handy to check for symmetry and light leakage but it will not play a major role. Yes, good cutting makes any gem look great but if it is coloured, then preserving the colour takes importance over everything else.

These tools are also geared for the characteristics of diamonds but with coloured gemstones, it will vary per each gem variety, so it will not work that well.

 

[MAC-W]

Thanks Chrono.

I'm assuming then that coloured diamonds come under the "Coloured" banner rather than the "Diamond" banner for these tools and technologies?

One other question....

I hear mention of something called a colorimeter, Is that something that could be used on gemstones or is that also just for diamonds?

 

[chrono]

FCD or fancy coloured diamonds falls mostly under CS because colour is also what sets the price. However, if it doesn't sparkle well.....
As you can see, cut is still important but lesser so than colour. Yes, a colorimeter is only for colourless diamond usage. It helps determine the "colourless-ness" (is there such a word? ) of "white" diamonds.