Help with grading coloured gems

[SparkleRx]

Hi Everyone,

Even after reading hundreds of threads I still have questions about coloured stones.

I understand diamonds pretty well (four C''s) and want GIA or AGS cert.

My question is what certification do I want and what stats do I look for for coloured gems? Does each gem require a different certification and stat? I am mainly interested in Tsavorite, Emerald, Sapphire, Spinel. But really would like to know what Certs and what stats to look for on all coloured gemstones.

Also, what do these terms mean and what are the ideal stats for each:

Brilliance (is 100% the best?)

Tone (what are the options?)

Saturation (what are the options?)

"AAA" (I saw that for a tanzanite and a tsavorite and don''t know what it refers to)

thanks!

 

[LD]

Coloured gemstones are graded differently from diamonds and are described as Types. Have a look at this for an overview.

http://www.multicolour.com/catalogue/source/cog.html
http://www.multicolour.com/catalogue/columns/column01003.html - this page gives a breakdown by gemstone and type

This explains, tone, hue, saturation etc:

http://www.multicolour.com/catalogue/source/clg.html

Each gemstone has, I think, what is considered to be the "best" combination but I believe it varies from gemstone to gemstone. Of course, your eyes are always the best indicators and you may not prefer the "best" combination!

Happy reading!

 

[PrecisionGem]

Colored stones are much different than spec-ing out a diamond. Buying a diamond is kind of like buying a tire. You spec out the size, color, clarity and shape, and then go shopping. Colored stones a whole different adventure. But ultimately, it boils down to what you find attractive. Sometimes you get lucky, and find that what you really like isn''t considered the ideal, and therefore ends up costing a lot less. Subtle differences in a colored stone, and impact the price dramatically.
Most stones, unless they are pretty expensive will not have a cert. But you can always get one. The AGL in NYC for example can do what they call a "Fast Track" for only $25 for most stones. This would tell you that the stone is real, and identify it, give you the dimensions and indicate most levels of treatment. If you want more information than this, then the prices go up.

Tone and saturation will vary for each type of stone, and these can be tricky to identify until you have seen lots of stones.

 

[Sagebrush]

Sparklers,

There is no easy shortcut to the connoisseurship of colored gemstones. It is about beauty not certification, thank God. Color, hue, saturation and tone is key. However, the "stats" differ for each color and each variety of gemstone. Much of it is explained in my book, so you can follow the link below and read a couple of chapters. Nothing, however, is a substitute for looking and comparing gems.

Best of luck,

 

[Pandora II]

Date: 11/5/2008 8:52:26 AM
Author: Richard W. Wise
Sparklers,

There is no easy shortcut to the connoisseurship of colored gemstones. It is about beauty not certification, thank God. Color, hue, saturation and tone is key. However, the ''stats'' differ for each color and each variety of gemstone. Much of it is explained in my book, so you can follow the link below and read a couple of chapters. Nothing, however, is a substitute for looking and comparing gems.

Best of luck,

Just wanted to add.. I''ve just got back from Sri Lanka where I spent quite a bit of time in Ratnapura buying rather a lot of new rocks. I took 3 books with me - Richard''s Secrets of the Gem Trade, the Gem-A Stone ID handbook and Antoinette Maitlin''s Identifying Gemstones.

I read the relevant chapters in yours many times before I got there Richard, and it certainly helped keep me focused and calm in the thick of things! Many thanks!

 

[Sagebrush]

Pandora,

Many thanks, book apparently did its duty. Worth the 40 bucks, I guess. I take it you are a buyer in the trade?

RW

 

[Harriet]

Date: 11/5/2008 8:52:26 AM
Author: Richard W. Wise
Sparklers,

There is no easy shortcut to the connoisseurship of colored gemstones. It is about beauty not certification, thank God. Color, hue, saturation and tone is key. However, the ''stats'' differ for each color and each variety of gemstone. Much of it is explained in my book, so you can follow the link below and read a couple of chapters. Nothing, however, is a substitute for looking and comparing gems.

Best of luck,

Richard, I couldn''t agree more.

 

[Pandora II]

Date: 11/6/2008 9:48:40 AM
Author: Richard W. Wise
Pandora,

Many thanks, book apparently did its duty. Worth the 40 bucks, I guess. I take it you are a buyer in the trade?

RW

Sadly not at the moment. Just a gem junkie and studying for my FGA...

I wanted to see how I did in the dragon''s den with what I''ve learnt so far - one of the most incredible experiences of my life. I''ll do a post sometime. I had everything tested in Colombo and all was well, so I''m pretty happy so far - now I just need to get my tutor and a few others to let me know what they think of my loot! Book worth every penny (and the added suitcase weight

)

Will definitely go back again - I suppose the next test will have to be Bangkok

, my husband is resigned to all holidays being in countries with gem buying opportunities!

 

[Sagebrush]

Pandora,

I''m jealous. Hopefully be in Asia early next year. Its the best part of the job.

Best of luck with your studies, you are doing it right, into the lion''s den.