CZ Master Stones Vs Diamond

[noobie]

How many appraisers still use real diamond master grading stones versus CZs? How reliable are the CZ stones and do they fade over time? How consistent is one set form the next




Anyone have a view on how accurate a colorimeter is as well? What do the major labs use? This question is sort of related to the great report leonid posted. I can understand clarity variance between labs, but color would seem more scientific. You would think that if they used properly calibrated master stones or colorimeters to double check then the color grading variability should be minimal. (unless the grader wears yellow sunglasses of course

)




How good are those $189 sets you can find on the internet?




I know, lots of questions.

 

[denverappraiser]

noobie,

Personally, I use diamond masters. Actually, in order to become an AGA certified lab, and AGS approved lab, or get any of the other laboratory credentials that I've seen, it is necessary to have a set of diamond masters. Most appraisers who take their trade seriously decide to invest in diamond masters. The problem is that CZ's simply don't look all that much like diamonds, especially in the table down position. The differences in the color grades are fairly discrete and it's important to be comparing apples and apples. CZ masters are not, in my opinion, sufficient to do a high quality job.

Neil Beaty, GG ISA
Independent Appraisals in Denver
www.gemlab.us

 

[norman_in_L.A.]

Noobie:




In our lab and appraisal offices we use diamond master sets for diamond color grading. We even have one set registered at GIA, master set #1521.




The Gemologist/Appraisers in our company that travel to customer sites use CZ master sets on these trips. Mainly because our insurance company will not cover the diamond master sets as a tool. So, in the case of a robbery the master sets would not be covered.




The CZ's do work quit well. Make sure that you use a 5000 kelvin light during the grading process. Kassoy sells what we think are the best sets (kassoy.com/diamgrad01.html) they offer a five year warrentee that we have taken advantage of several times.




As far as the Colorimeter goes, most labs have at least one on site. The Colorimeter is only a tool that we use during the color testing, it does not nor do we use it to assign the golor grade. It is really helpful when grading color in a brown or yellow brown diamond. It will split out the two colors for the diamond color grader.




I hope that this information will be of help to you!




Norman

 

[blitz]

I use a set of 5 master diamonds (GIA certed). I bought one diamond every year to complete the set.

 

[noobie]

Thanks,




For some reason I was under the impression that CZ grading stones were becoming more popular and they did fade, but there are differing opinions as to how much a problem it is.




With the five stone sets that skip a grade, for example E,G,I,K,M, how accurate is it to grade the colors in betwwen and when they are a stong F or weak F.




How much are a set or real diamond masters anyway?




BTW, I have no intention of getting into the trade, I was just curious, since color has a large effect on price and it does seem to be variable to some degree. Also had a five minute thought of buying a set CZ's to play with, but then figured another toy to collect dust!

 

[denverappraiser]

noobie,

They're extremely popular ... and they do fade. They are popular for one and only one reason. The price. Diamond masters must be specially graded by either GIA or AGS as masters (regular reports don't qualify) and they are quite picky. GIA rejects something like 90% of the stones submitted. The stones need to be more or less the same size, at least VS with a very good to excellent cuts. You can use the PS database to get a feel for pricing but it's easy to find yourself spending thousands of dollars EACH to build a set of masters.

Neil Beaty GG ISA
Independent Appraaisals in Denver

 

[WinkHPD]

Diamonds here. 5 stone set with both AGS and GIA registration. Boiled in acid every so often to keep the tweezer metal from causing the stone to darken. (Children, do not try this at home!)

Wink

 

[blitz]

Thank you for the cleaning tip!
Most of my grading (color) is for diamonds within a mounting. If I was to start grading 20% or more loose, I would begin to purchase the in-between diamonds.
I would like a Z color diamond to assist with the cut-off for fancy color.

 

[WinkHPD]

You are welcome. Many people do not regularly clean their diamonds and this can adversly affect the accuracy of their grading. I had a man whom I respect for his knowledge in this area tell me that he has seen G colored master stones that were I color because of the metal picked up in the girdles by years of handling. This is especially true in girdles that are not faceted.

Wink

 

[fire&ice]

What size do they have to be?

 

[StevL]

We have both, the diamond set we have had for years (20 or more) and the CZ set about a year. To be very honest the CZ set works just fine. But... the CZ set needs to be kept in total darkness when not in use, this will protect them from fading. We will be sending our CZ set back every two years just to have them checked and adjusted if needed. I believe the manufacturer suggest to do that.

 

[wanderlost]

I'm curious to hear whether this hot-acid cleaning process (or timed reference (eg. ref. std. to be re-cert'ed 12 months from received date/from last verification) to a 'Master master set' (or just another certified master set) is a process that the other appraisers (or owners of diamond master sets) do....

In addition, I'm curious as to why (other than being cost-prohibitive) extremely sensitive colorimeters are not used rather than eyeballs. It seems that even an 'ancient' spec-20 (properly calibrated) could give valid & reproducible numerical data.....(and these are not cost prohibitive at all).

 

[denverappraiser]

Wanderlost,

I don't know any consumers that acid clean their diamonds but it's fairly common in the labs and among appraisers. It's important that both the stone being graded and the master be clean in order to properly match them.

Colorimeters are getting better but they still have quite a few issues surrounding them. They tend to respond differently to fluorescence and to different sizes and cuts of stones but the so do gemologists. I must admit that I don't understand why they can't seem to get it right. Actually, they are a fair amount cheaper than master stones and customers tend to like the technical feel that they add so most jewelers would be tickled to get one that was reliable. Are any of the manufacturers watching this forum who could give us the lowdown on why this is so difficult to accomplish?

Neil Beaty GG ISA
Independent Appraisals in Denver
www.gemlab.us

 

[noobie]

----------------
On 8/9/2004 3:08:06 PM denverappraiser wrote:





Colorimeters are getting better but they still have quite a few issues surrounding them. They tend to respond differently to fluorescence and to different sizes and cuts of stones but the so do gemologists. I must admit that I don't understand why they can't seem to get it right. Actually, they are a fair amount cheaper than master stones and customers tend to like the technical feel that they add so most jewelers would be tickled to get one that was reliable. Are any of the manufacturers watching this forum who could give us the lowdown on why this is so difficult to accomplish?

Neil Beaty GG ISA
Independent Appraisals in Denver
www.gemlab.us

----------------

Yes, that was part of my original question although it's more clearly stated. If they get it right we wouldn't have these subjective soft color grades and we could all just discuss the variances in clarity (or why one colorimeter is more accurate than another

)

As a follow-up, do most appraisers use five master stones or ten?

 

[denverappraiser]

As a follow-up, do most appraisers use five master stones or ten?

Most don't have any, they use CZ's. Personally I have 8. E-F-G-H-I-K-L-N. I'm building up to 10 but that money thing keeps getting in my way. Like Jennifer, I would love to find a Z. I have a 10 stone CZ set as well. I think 5 is sort of the minimum to declare that you have a set of diamond masters an get taken seriously by AGS and similar organizations. If you're going to use CZ, you might as well use 10.

Neil Beaty GG, ISA
Independent Appraisals in Denver
www.gemlab.us

 

[noobie]

----------------
On 8/9/2004 7:46:13 PM denverappraiser wrote:





Personally I have 8. E-F-G-H-I-K-L-N. I'm building up to 10 but that money thing keeps getting in my way. Like Jennifer, I would love to find a Z.

----------------

Thanks, just out of curiousity why I-K-L-N and not I-J-L-N? Do you come across more K stones than J?

 

[denverappraiser]

I just haven't found my J yet. The N just came along and it was cheap enough that I couldn't say no. The next 3 are D-J-Z.

Neil Beaty GG ISA
Independent Appraisals in Denver
www.gemlab.us

 

[fire&ice]

Will anyone satisfy my curiousity as to how big these stones need to be? I doubt whether a .10 stone is gonna do it; yet, I am sure you don't need a big honker either.

 

[denverappraiser]

Mine range from 0.58-0.63cts. each. I'm pretty sure that GIA uses 1.0cts. each. The smallest that GIA-GTL will grade as a master stone is 0.25cts. and they will only allow a 0.10ct variation throughout the entire set. In general, bigger is better.

Neil Beaty GG, ISA
Independent Appraisals in Denver
www.gemlab.us

 

[fire&ice]

----------------
On 8/10/2004 11:17:01 AM denverappraiser wrote:

Mine range from 0.58-0.63cts. each. I'm pretty sure that GIA uses 1.0cts. each. The smallest that GIA-GTL will grade as a master stone is 0.25cts. and they will only allow a 0.10ct variation throughout the entire set. In general, bigger is better.

Neil Beaty GG, ISA
Independent Appraisals in Denver
www.gemlab.us
----------------

Thank you! It does make sense.

 

[noobie]

The CZ grading stones I saw looked to be 1 carat in size or maybe even slightly bigger. I guess with CZ you can get whatever size you want.

 

[blitz]

Oh my! Now I have to start buying a stone a year again. I'd rather wear one then keep it in its little white box, but this discussion was good because it made me think and re-act.
Gracias