How are colored stones graded differently than diamonds?

[Daisi2112]

I''ve learned so much about diamonds on PS that now I am curious how colored stones are graded. Are they graded the same as diamonds or differently?

Thanks!!

 

[MakingTheGrade]

There really isn''t even a standard grading system for colored stones since there''s such a range of colors, tones, saturations, etc.

Individual sellers will have their own grading scales, but if you send something to get certified by the AGTA, the certificate doesn''t come back with meaningful numbers or letter like in diamonds, it''s usually just a description of the stone and disclosure of treatment.

It''s why I think buying colored stones is trickier, but also much more fun

 

[Kismet]

The thread here has a nice intro into colored stones.

 

[chrono]

Very differently from diamonds. Coloured stones are all about colour and there is no grading for cut. Even within colour, there are a lot of nuances. Most labs will only state the colour but AGTA and AGL will give more details about brilliance, undertone, etc if you get the full lab cert.

 

[Daisi2112]

Date: 4/30/2009 9:11:38 AM
Author: Chrono
Very differently from diamonds. Coloured stones are all about colour and there is no grading for cut. Even within colour, there are a lot of nuances. Most labs will only state the colour but AGTA and AGL will give more details about brilliance, undertone, etc if you get the full lab cert.

So if there is no grading for cut, how do you know you''re buying a really good quality colored stone? Are there certain cuts that just look good with certain colored stones? Sorry, I''m so confused!

 

[Kismet]

Date: 4/30/2009 10:29:09 AM
Author: Daisi2112

Date: 4/30/2009 9:11:38 AM

Author: Chrono

Very differently from diamonds. Coloured stones are all about colour and there is no grading for cut. Even within colour, there are a lot of nuances. Most labs will only state the colour but AGTA and AGL will give more details about brilliance, undertone, etc if you get the full lab cert.

So if there is no grading for cut, how do you know you're buying a really good quality colored stone? Are there certain cuts that just look good with certain colored stones? Sorry, I'm so confused!

You'll know because of the really good COLOR! Forget what you learned about cut because with colored stones it's all about the color.


ETA: Ok, not *all* but mostly about color. Since colored stones all vary by type, there's no one standard for cut, color or clarity. Also, since carat is a weight and not a volume, you can't compare a carat of sapphire or whatever to a carat of diamond... compare mm size instead.

 

[chrono]

Colour trumps all in gemstones. Cut counts for very little. There are desired sweet spots for every gemstone family and type. If you think finding a good diamond is difficult, it is 10x worse in gemstones. There is no desired cut or shape for any gemstones.

 

[Lady_Disdain]

Buying a diamond is very much like buying a commodity: you check the stats and the numbers pretty much tell you what the stone is like. This why buying a diamond online isn''t that hard.

However, coloured stones are much harder, since there are so many more variables. For example, there are many more different cuts, with interesting patterns, different angles, etc. In coloured stones, there is even a discussion on whether a cut that doesn''t follow the critical angles for the stone type can actually improve cost. A diamond is cut for fire and scintillation, generally speaking. A coloured stone can be cut to maximize sparkle or colour or weight or to hide an inclusion.

Colour is both a personnal choice and an important factor in price. An "ideal" or text book colour will cost more. If you are lucky, you will find you like a less desired shade!

Even inclusions are treated differently: some kinds should be absolutely clear, other can benefit from inclusion (silk can cause a stone to glow or horsetails in demantoids, jardin in emeralds) and some kinds of stones (type 3) just naturally have more inclusions. For example, finding an absolutely clean Paraiba is near impossible (and too expensive!).

I think you should look around a lot, read the board and choose what kind of stone you are looking for (sapphire, spinel, tourmaline, etc). Then read up on your chosen type and learn how to shop for it. There really isn''t a one size fit all formula.

 

[chrono]

Cutting is of paramount importance in colorless diamonds because if a colorless diamond doesn’t have interesting faceting or precision cutting, it won’t have a lot of rainbow coloured sparkle. However a stone with color, while I do think cut is important, color should be paramount because you can always have it recut. Precision cutting is nice, but not a necessity like it is in a diamond.

 

[T L]

That's so true Chrono. For example, cabachons aret are not faceted at all, but are used to display pure color. Can you imagine a cabachon diamond?

Diamonds are really known for their amazing refractive properties, so to take advantage of that, cutting is probably one of the most important things to consider. I have some poorly cut colored gems with great color, and the cutting doesn't bother me as much because it's all about the color.

 

[FrekeChild]

I love me some precision cut.

 

[Lady_Disdain]

Date: 4/30/2009 5:29:33 PM
Author: tourmaline_lover
That''s so true Chrono. For example, cabachons aret are not faceted at all, but are used to display pure color. Can you imagine a cabachon diamond?

Diamonds are really known for their amazing refractive properties, so to take advantage of that, cutting is probably one of the most important things to consider. I have some poorly cut colored gems with great color, and the cutting doesn''t bother me as much because it''s all about the color.

I once saw some cabochon demantoid and sphene. That is a waste of good RI (refractive index).

 

[T L]

Yes, I wouldn''t want a badly cut demaintoid, sphene or sphalerite either. Those three gems are more about their dispersive properties than color (except for super fine chrome green Russian demantoid)

 

[chrono]

When a gem stone has excellent colour but poor clarity, it is usually cabbed to make the best of the rough. If faceted, even if precision cut, will show hideous inclusions that will detract from the overall look, and possibly bring the value down. Sometimes the cutter just tries his best to work with what nature gives him.

 

[PrecisionGem]

Of course you all knew I would pipe in and disagree.

Cutting is very important in colored stones. In R.W. Wise''s book, he says; "there are many well cut stones that are not ''gems'', but there are NO ''gems'' that are not well cut."

A well cut stone, all other things being equal will be more beautiful, and will sell for a higher price, and be more rare. For every thousand of poorly cut stones, there is maybe 1 well cut one. The more unique cuts, attract the more unique jeweler, who make the more unique, one of kind (expensive) piece of jewelry.

How many times on Pricescope have we heard someone who bought a stone from one of the US cutters say "wow, it sparkles so much" or something along those lines. They are comparing these well cut stones, to the other commercial cut stones, and see a difference. I have seen a few stones posted here that are recuts, and the difference is dramatic. Some guys make a living buying cut stones and recutting. Even though the finished stone is smaller, they are selling them for a higher price. Why? It''s because of the added beauty of the better cut.

 

[FrekeChild]

I'm with Gene on this one. But I think everyone knows I'm a big advocate for precision cut stones...

What can I say? I love me some sparkle!

 

[chrono]

Date: 4/30/2009 10:51:17 PM
Author: PrecisionGem
Of course you all knew I would pipe in and disagree.

Cutting is very important in colored stones. In R.W. Wise''s book, he says; ''there are many well cut stones that are not ''gems'', but there are NO ''gems'' that are not well cut.''

A well cut stone, all other things being equal will be more beautiful, and will sell for a higher price, and be more rare. For every thousand of poorly cut stones, there is maybe 1 well cut one. The more unique cuts, attract the more unique jeweler, who make the more unique, one of kind (expensive) piece of jewelry.

How many times on Pricescope have we heard someone who bought a stone from one of the US cutters say ''wow, it sparkles so much'' or something along those lines. They are comparing these well cut stones, to the other commercial cut stones, and see a difference. I have seen a few stones posted here that are recuts, and the difference is dramatic. Some guys make a living buying cut stones and recutting. Even though the finished stone is smaller, they are selling them for a higher price. Why? It''s because of the added beauty of the better cut.

I agree with that statement. I have seen some well cut gems with mediocre colour and some good native cutting with superb colour. Personally, I prefer to get an excellently coloured gemstone with above average cutting. It doesn''t need to be precision cut but it must have a good outline, no windows, little extinction, something not lopsided, centered culet, ...you get the idea.

 

[T L]

Well, I think in this case, a picture speaks a thousand words. Here's Anita's Richard Homer recut of her cuprian tourmaline. In this case, I think the recut definitely helped. Every case is individual though. Some stones lose saturation upon recuts, and I also think the outcome highly depends on the skill of the cutter as well.

 

[Daisi2112]

Wow, those pictures are great! Thank you!