GIA Grading of

[maxspinel]

I am trying to understand the colored stone grading standard of GIA and I get confused

. Tone is defined from 1 to 8; 3 is light, 5 is medium, 7 is dark. Saturation is also from 1 to 8.

Pink is actually red with less saturation. So for pink sapphire, is it a lighter tone red, or a lesser saturated red, or both.

For a top quality "vivid" pink sapphire, shoud the GIA denotion be R3/3, R3/6 or R6/3?

I do know it is not R6/6 since this is for nice rubies.

 

[colormyworld]

Hello Maxspinel. I am pretty sure GIA grades for tone are from 0 to 10, saturation is from 1 to 6. As for pink sapphire. I think tone and saturation are 4 or under. If you do a search with GIA saturation scale as your keyword you may get more info. I am not an expert so take what I say with a large grain of salt. Regards Doug

 

[valeria101]

GIA's color scales are lined up HERE pretty well.

The shop uses them, so you could find pink 'examples' among their fare, as much as feasible online.

There must be others and better, this one just came up - I didn't even know they have that page until 5 min ago.


If you have a bit of time to burn, try out CIGEM's detailed explanation, Java color coding exercise & all

There's a link from the to Stuller's Gem Wizard page - a playful thing that lets you combine tone with saturation levels on GIA scale and generated little pictures to show you what that might mean.


Hope this helps with the system. How much this helps choosing a pink sapphire is yet another Q and I am not very sure of the answer there.

 

[colormyworld]

Cool site Ana.

 

[Sagebrush]

I don''t work with GIA terminology much but you are correct; pink is a lighter toned less saturated red.

 

[bar01]

Here are some examples of GIA graded pink sapphires. This site also has some nice discussions of GIA system.


Also this may be of interest in discussing the line between pink sapphires and rubies.

 

[maxspinel]

Date: 10/5/2005 9:51:25 AM
Author: Bertrand
Here are some examples of GIA graded pink sapphires. This site also has some nice discussions of GIA system.


Also this may be of interest in discussing the line between pink sapphires and rubies.

Hi Bertrand,
They are interesting sites so I pulled out the grading of some rubies and pink sapphires and they are still confusing. The rubies are pretty straight forward; they look red in the picture and are graded R, slpR, StpR with 5/6, 6/6.

However, the pinks are a mixed bunch; hue is graded similar to the rubies as R, slpR, stpR but tone/saturation varies as 2/3, 3/4, 4/4, 5/5. The medium dark tone/ higher saturation such as 5/5 are more expensive. It seems like anything that doesn''t look red get thrown in as the pinks. Some pinks are graded as slpR, stpR (slight or strong purplish red), the same as some rubies but the color look really different. One ruby graded as slpR6/5 looks red but one pink sapphire graded as slpR5/5 looks purple

. Does the GIA standard really work in identifying color?

 

[colormyworld]

Hi maxspinel, Love that handle BTW I think the first # is for tone. If it is darker than a certain tone ( I think 4 ) It is either a purple sapphire or a ruby. I think the best tone, sauration for pink sapphire is 4/4 I think a lot of your confusion is because of what some people are calling " pink sapphire ". IMO. A lot of what is called pink sapphire is just lighter tone/ saturation purple sapphire. That is IMO. Doug

 

[valeria101]

Date: 10/7/2005 7:57:54 PM
Author: maxspinel

The rubies are pretty straight forward; they look red in the picture and are graded R, slpR, StpR with 5/6, 6/6.

Some pinks are graded as slpR, stpR (slight or strong purplish red), the same as some rubies but the color look really different. One ruby graded as slpR6/5 looks red but one pink sapphire graded as slpR5/5 looks purple.

I am no expert, but would like to take a stab at this...

There are a few things to look at:

#1. A problem with the example:
those examples are merchandise graded by a shop and all we see are pictures. Hopefully they graded the gems not the photos, and there may be several layers of distortions between what the grades are intended to mean by GIA, what they were meant to show by the shop and what the pictures on the screen look like. All in all, not the best place to learn how to read the grades. Perhaps they didn't even do the sort of consistency check of their website as you did and would be terrified at the sight of this thread!

#2. Another problem with the system...
It is not intuitive to analyze those colors, but as far as I understand, the overall 'look' in laymen words (such as 'red' and 'purple') is determined by all three components of the color grade (hue, tone and saturation) so not all things with hue 'R' are red. You wrote that 'all that is not red is pink' - well, maybe that is what the respective website happened to have in their inventory, if there was a piece stpR 7/2 maybe they would not have listed it! (think dark gray spinel). I am not surprised by your interpretation of the purplish red things with more or less saturation - it is a usual thing to call saturated redish stuff 'red'. So do I and everyone else I know. It takes allot of blue in saturated purple to get people calling it anything but 'red' at first sight, unless that is a gathering or gem or rose collectors

Less saturated pure red might be called 'pink' or 'dark pink' and if there is some other component in hue it would be noted more readily... like you did.

#3. So...
To clarify how these color names work, it may help to forget all intuitive notion of color, imagine you are on a new planet and look at an automatic generator of color grades, not pictures of gems. The page at Stuller has one (The Gemwizard) and a large database of examples. I have no idea what else the thing is good for, but it lets you select hue, tone and saturation and delivers a small picture of a facet map colored that way. You can line up a few in different traditional shapes. It helps a ton explaining what the color codes mean.
Just IMO.

I've had my doze of puzzlement with this color system got to the current conclusion and then never looked back again. It may be useful to know how it works just in case you find a seller who uses it. And the codes are useful to help two people talk approximately about the same thing... to some extent.


And this is why I am not a fan of the color grades...
Perhaps I just do not understand it right, but... it seems that the system is good only for a limited range of colors that are known to be meaningful. So if you know gems, you know what the codes mean but the other way around may not always be true and this makes the color grades a poor communication tool. For once, does every hue & tone & saturation set have a meaning? For example, what happens with high saturation and light tone? Or the other way around... If these combinations are not feasible as a visual impression, than, IMO, the analytic components of the color grading scheme are not independent of each other, which makes them redundant as descriptors and qualifies their combination (i.e. the good old color words in English) as a more handy tool. Not to mention allot less confusing.

 

[colormyworld]

Some of the stones have grading reports. None of them appear to be graded by GIA. A GIA trained gemologist perhaps. Two have AGL reports, both are listed as rubies. The others look like appraisls. All should be taken with a grain of salt as they are all opinions. I do have much more faith in the AGL reports though. I do wonder why some of the more expensive stones do not not include AGL reports. Regards Doug

 

[colormyworld]

According to the source I have Pink sapphire is strongly purpleish red, slightly purplish red and red. While purple sapphire is bluish purple, purple, reddish purple, and purple red. I also notice the site linked to above is calling a#3 saturation moderately strong but that is really a #4 saturation. They also call #4 saturation a strong when that is a # 5 To me this makes me question their grading of hue also, as to accuracy IMO. Hope this helps Regards Doug I have made a big mistake on my assesment on what is considered pink sapphire. After further research I have discovered that in the red hue the saturation can be as much as 6 witha tone of 4. In the slpR hue saturation can also be 6 with a tone of 4. In stpR hue the saturation can also 6 with a tone of 4. These are with a tone of 4 except the red where if the saturation is lighter the tone can be up to a 5. I was also incorrect about PR/RP where tone can be a 4 with a saturation up to a 6 Also rP can also have a tone of 4 with a saturation of 6 I even see that purple with a tone of 4 and a saturation up to five is considered pink sapphire. Yum yum this crow tastes good .

 

[maxspinel]

Date: 10/8/2005 9:23:14 AM
Author: colormyworld
According to the source I have Pink sapphire is strongly purpleish red, slightly purplish red and red. While purple sapphire is bluish purple, purple, reddish purple, and purple red. I also notice the site linked to above is calling a#3 saturation moderately strong but that is really a #4 saturation. They also call #4 saturation a strong when that is a # 5 To me this makes me question their grading of hue also, as to accuracy IMO. Hope this helps Regards Doug I have made a big mistake on my assesment on what is considered pink sapphire. After further research I have discovered that in the red hue the saturation can be as much as 6 witha tone of 4. In the slpR hue saturation can also be 6 with a tone of 4. In stpR hue the saturation can also 6 with a tone of 4. These are with a tone of 4 except the red where if the saturation is lighter the tone can be up to a 5. I was also incorrect about PR/RP where tone can be a 4 with a saturation up to a 6 Also rP can also have a tone of 4 with a saturation of 6 I even see that purple with a tone of 4 and a saturation up to five is considered pink sapphire. Yum yum this crow tastes good .

I tried to summarize what you posted to be what is considered to be good saturated pink sapphire:

R4/6, 5/5; SlpR4/6, 5/5; StpR4/6, 5/5; rP/pR 4/6; P4/6

Well, this pretty much includes everything that is not a ruby R6/6, 5/6

. There are debates on guidelines what is a ruby vs. a pink sapphire. It seems like there is also a gray area between a pink vs. a purple sapphire. This is why I am always having problems buying a stone via the internet. Color is the most important aspect and you can''t see it via a monitor and you can''t rely on a grading system. So if you can''t check it out in person, the chance of success is minimal.

BTW, I am wondering how the AGL system is comparing with the GIA and are they more accurate?

 

[colormyworld]

That sums it up pretty well as for top colors. I guess it really comes down to what suits each persons tastes. regards Doug

 

[valeria101]

Date: 10/9/2005 1:25:28 PM
Author: maxspinel


So if you can''t check it out in person, the chance of success is minimal.

Perhaps the sellers are just as desperate as you to pass the right message, and there is always some return policy, so that you can check things in person one at a time. If what you are looking for is not common, there may not be many opportunities to see more than one at a time anyway because of scarce inventory.

Even if you do look for acurate color grading, how will you know what a certain grade looks like?

Anyway, I may still defend traditional communication over precise technical grading as color grading is for now.

How bad can it be ?

 

[strmrdr]

I think establishing a relationship with a dealer is much more important than a bunch of numbers or words on a web page.
Iv bought enough gemstones from Gary aka diamondexpert that he knows what I like and I know how he thinks when it comes to describing colors.
Thats why if I was buying an expensive stone or any stone that is one Id be picky about the color of Id go thru him.
And most importantly he is honest and has a great return policy.
He has earned my gemstone business even if it costs me slightly more than going thru some of the overseas vendors.

 

[cflutist]

Date: 10/5/2005 1:39:40 AM
Author: valeria101

GIA's color scales are lined up HERE pretty well.

Ana, great link on the Multicolour stie to the color descriptions.

There is 27 page booklet of Color Grading Charts that was part of the GIA Colored Stone Grading Course I completed back in 1989. There are girds of Tone/Saturation combinations for the various hues of a certain species. On each of the grids are rankings for the various Tone/Saturation combinations - from 0.1 (worst) to 10 (best) and everything in between.

There are 6 different grids for Pink Sapphire:

1. R - R 4/6 = 6.4, R 4/5 = 4.5, R 2/1 = 0.1 (there are more but only showing best/worst)

2. slpR - slpR 4/6 = 6.4, slpR 2/1 = 0.1

3. stpR - stp R4/6 = 9.4, stpR 3/6 = 8.1, stpR 4/5 = 5.9

4. RP/PR - RP/PR 4/6 = 10.0, RP/PR 4/5 = 7.6

5. rP - rP 4/6 = 10.0, rP 4/5 = 7.6

6. P - P 4/5 = 5.9

So according to the GIA Colored Stone Grading Charts (1989), GIA assigns the highest grade for Pink Sapphire as
RP/PR 4/6 or rP 4/6 both which are assigned a 10.

This is followed by stpR 4/6 at 9.4, then stpR 3/6 at 8.1, then RP/PR 4/5 or rP 4/5 at 7.6
which is better than any tone/saturation combinations of R, slpR, or P.

Hope this helps.

 

[cflutist]

Date: 10/9/2005 1:25:28 PM
Author: maxspinel
I tried to summarize what you posted to be what is considered to be good saturated pink sapphire:

R4/6, 5/5; SlpR4/6, 5/5; StpR4/6, 5/5; rP/pR 4/6; P4/6

Let me look these up for you on the GIA Color Grading Charts:

scale 0.1 worst to 10.0 best.

R4/6 = 6.4 on a Pink Sapphire Chart

R 5/5 = 1.6 on a Ruby Chart (not listed as a Pink Sapphire)

slpR 4/6 = 6.4 on a Pink Sapphire Chart

slpR 5/5 = 1.6 on a Ruby Chart (not listed as a Pink Sapphire)

stpR 4/6 = 9.4 on a Pink Sapphire Chart

stpR 5/5 = 5.9 on a Purple Sapphire Chart

RP/PR 4/6 = 10.0 on a Pink Sapphire Chart

P 4/6 = not listed on Pink Sapphire or Purple Sapphire Chart, however P 6/6 is an 8.1 and P 5/6 is a 6.4 on the Purple Sapphire Chart, and P4/5 is 5.9 on the Pink Sapphire Chart.

 

[maxspinel]

Date: 10/16/2005 11:42:39 AM
Author: cflutist

So according to the GIA Colored Stone Grading Charts (1989), GIA assigns the higest grade for Pink Sapphire as
RP/PR 4/6 or rP 4/6 both which are assigned a 10.

This is followed by stpR 4/6 at 9.4, then stpR 3/6 at 8.1, then RP/PR 4/5 or rP 4/5 at 7.6
which is better than any tone/saturation combinations of R, slpR, or P.

Hope this helps.

Thanks a lot Cflutist. I am now taking the GIA "Colored Stone Essentials" via distance studies and the "Colored Stone Grading" extension course will be my next year''s project. I am not trying to become a gemologist, just accumulating more knowledge so I can be better equipped for my next purchase.

It is interesting that GIA will assign a 10 to RP/PR. I always thought too much purple will make the stone less pink or red, and less valuable.

 

[cflutist]

Date: 10/16/2005 12:46:08 PM
Author: maxspinel
It is interesting that GIA will assign a 10 to RP/PR. I always thought too much purple will make the stone less pink or red, and less valuable.

MS, please go back and look at the link that Valeria provided. If you look at hues RP/PR and rP, I would they are pretty desirable for what I would want a Pink Sapphire to look like (well at least on my computer monitor). When I was in the market for a Pink Sapphire several months ago, I found that the ones closest to these hues had the highest price per carat on the Palagems website.

The link that Valeria provided also mentioned that the GIA GemSet® has 324 sample hue colors with varying Tones and Saturations. I don''t think GEM Instruments sells that set anymore, but I did find a flyer in my GIA Colored Stones Grading Class binder that said they were $585 - $650 at the time depending on which set you bought.

Glad to hear you are taking GIA Distance Learning classes. Like you, I took the classes for my own enrichment at the time
because 1 - I wanted to know more about what I was buying and 2 - the Internet and education sites such as Pricescope did not exisit in 1986 - 1989. I thought of it like the Consumer Reports of diamond/gem buying.

I don''t work full time in the jewelry business (am a VP in the IT business) but do keep up by subscribing to trade journals such as JCK and National Jeweler.