Problem found when using cut advisor?

[mmlaw98]

I found a nice .9ct H VS2 (H&A) diamond at Whiteflash.com, but when I input its attributes into the cut advisor it tells me that the depth is incorrect or that the girdle is overly thick; however, the certificate for the stone indicates that the girdle is thin to medium faceted. Hopefully, one of you guys can shed some light on this situation. Here are the stones measurements:
T=57; D=62.5; Crown ang=35.5; Pavilion %=41%; overall dimensions 6.14-6.18*3.85.Thanks.

 

[drewg350]

Leonid, you are a constant inspiration to the consumer. I value your answers greatly and appreciate your unbiased opinions. You have a great way of not talking down to the average "Joe". Thanks, keep up the great work!!!!

 

[lawmax]

 

[Garry H (Cut Nut)]

Hang on - 42.9% does not equal 41 degreesanyway forget the stone - it is not great.
garry

 

[pricescope]

Thanks Drew

 

[pricescope]

Garry, that is the case when Sarin angles and % don't ad up.Would you post here about Sarin measurements details, please?

 

[pricescope]

OK. It was confirmed that the pavilion depth should be 42.9% - 41 is the pavilion angle.

 

[mmlaw98]

Leonid,Thanks for getting to the bottom of that measurement situation for me. I guess your concern regarding the crown angle was well placed; I input all the attributes into the cut advisor and it came up as a 4.1 (good only if price is a factor- the stone is advertised as H&A). It is truly amazing how difficult choosing a diamond can be, if one is interested in quality over quantity. Thanks again.

 

[pricescope]

Mmlaw98, it seems like a very rare case for this brand when cutter should chose whether to save a weight and keep it within certain range - 0.9 ct.I am surprised myself to see this example. As far as I know A Cut Above brand is on of the best and consistent H&A available today. Most of their stones are rated excellent by the HCA.Don't give up, you already know more than average diamond sales person. There are still plenty of great diamonds out there

 

[Garry H (Cut Nut)]

Accuracy of Proportion Measurement Instruments
Two manufacturers that specialize in proportion measuring devices are Sarin Technologies and Ogi Corporation.
The base models of both have a limited accuracy. More accurate models have different sized ‘windows’ that make it possible to use a larger portion of the field of view to measure different size stones. The most advanced models have a multiple lens capacity within the same unit, so the most appropriate lens can be used for an individual diamond.Measuring a 3mm stone with a lens designed to measure 20mm diamonds will reduce the accuracy by a factor of three compared to using a lens designed for a 7mm maximum stone diameter.
Another problem is the fact that Sarin proportions often do not add up to an accurate total depth as calculated by dividing depth by diameter. There are several reasons for this, however the solution applied by Ogi is to adjust the other parameters to equal the known weight. This is akin to a surveyor adjusting rise and fall measurements to ‘close the loop’. This approach adds an error to at least one or more of the measured proportions, rather than accepting the best assessments of the instrument. While it is difficult to explain this error, it is one of the likely reasons why all the major laboratories choose Sarin over Ogi.
Used properly a well-calibrated Sarin measures to an accuracy of 20 microns and gives results to within 0.2 degree. This level of inaccuracy will provide significantly different results using the Cut Adviser at Pricescope, but this is a constraint faced by all cut grading systems. The most positive comment that can be made is that the most accurate facet measurement is the pavilion facet angle. This is because it is the longest measurement made and the methods employed measure inclination more accurately. The same method is used for short facets, the inclination is measured and interceptions are plotted, so the shorter the distance between two points on the facet edge being analyzed, the greater the margin for error. The pavilion angle has been is the single most critical proportion on a diamond. It is four or five times more critical than crown angle or any other proportion in its effect on diamond beauty.

 

[pricescope]

Mmlaw98, I sent an email about this problem to Whiteflash a while ago - no reply yet.If you are still curious about this diamond you can just call them: 1-877-612-6770.They are nice and knowledgeable so you'll get all info you need.leonid

 

[pricescope]

Mmlaw98, You are right. It looks like there is a typo. I don't think that 41% is a correct number - it is too little and outside of AGS0. It looks more like pavilion angle value.I also concern about 35.5 crown angle - too steep.I'll send this topic to Whiteflash and ask to clarify thisleonid