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GIA versus Megascope measurments


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I am in a process of buying Round Brilliant Diamond from online seller.

After I selected 3 C's, symetry and polish excelent and cut Ideal I found out I can afford somewhere around 0.42 Carat (Price around 1070$). All diamonds have GIA certificat.


Since I had only 3 diamonds to select from I asked the seller for additional information (crown and pavilion angle). For my diamonds I got scanned megacsope reports (it looks like they are Sarin computerized proportions measurements) with no indications that it goes for the same pieces (no GIA No. on the report for specified diamond or carat weight)


After I checked them carefully I found some deviations from GIA reports.


For example:


Data for the first diamond

GIA report 4.81-4.85x2.99, weight 0.42 carat, Depth 61.9%, Table 56%, Girdle Medium, Faceted, Culet none

Sarin report: 4.84 (4.81-4.88) x 2.99, Depth 61.3%, Crown angle 34.2 deg, Pavilion angle 41.0 deg, Table 2.63 (54.4%), Culet 1.1% V. small, Girdle 1.7% (1.0-2.2)%




Data for the second diamond

GIA report 4.84-4.88x2.93, weight 0.42 carat, Depth 60.3%, Table 57%, Girdle Thin to medium, Faceted, Culet none

Sarin report: 4.87 (4.84-4.89) x 2.93, Depth 60.2%, Crown angle 33.7 deg, Pavilion angle 40.6 deg, Table 2.71 (55.7%), Culet 1.3% Small, Girdle 2.0% (1.6-2.4)%




Data for the third diamond

GIA report 4.77-4.82x2.97, weight 0.42 carat, Depth 61.9%, Table 57%, Girdle Medium, Faceted, Culet none

Sarin report: 4.80 (4.77-4.85) x 2.95, Depth 61.5%, Crown angle 34.3 deg, Pavilion angle 41.1 deg, Table 2.77 (57%), Culet 0.7% Very small, Girdle 1.8% (1.0 thin -2.2 sl. thic)



When I was comparing Culet and Girdle GIA vs report I found out pretty big diference. (does GIA classify small culet as none?)


Are this kind of deviations possible due to meter’s mistakes or are there some discrepancy? I have certain doubts regarding this measurments because crown and pavilion angle all match AGS IDEAL cut...


Thanks for any help on choosing the better one…


Best regards,

Matjaz Lapan

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Why do you need the sarin information? Is it because people on the internet are trying to tell you that you need this info? External averages don't tell you how beautiful a diamond is. For this you need to see the diamond. Someone trying to tell you how a diamond will look by just a few numbers, and they haven't seen it ,is like the blind leading the blind.


For the last few years, there has been a system that claims to give visual performance of diamonds it never sees based on punching in a few numbers which are then spit back out as supposedly accurate visual results?!


Some consumers may have become familiar with this since it is preached as gospel on a particular forum that markets this system. I will give you some of the reasons why this system does not work in giving accurate visual performance of diamonds.


1. First and most obviously, the diamond is never *seen*, so how can visual results be given? They can't. No gemological laboratory or professional would ever render opinions, and especially visual opinions, on something that it never sees. It starts off inaccurate from the get go. This should be common sense.


2. It is relying on mathematical external averages of only a portion of the diamond that it is supposedly giving visual results of? An average crown angle, pavilion angle, table and total depth cannot render the total visual possiblility of a diamond. There are 57 facets on a round brilliant diamond to begin with. The total external overall picture of the diamond is not even taken into account. Even if it did, it would not matter because the physics of light passing through a diamond and returning to the eye for maximum brilliance cannot be summarized using average measurements by a simplistic formula that is alleged to cover the "visual truth" over a wide spectrum of diamonds. This is so obvious with just a little bit of thought. There is an almost uncountable number of beams of light entering a diamond through each facet of the stone. How can any tool even approximate the visual "beauty" of a diamond when it does not take into account all the facets the beams of light enter from? Let alone the incredible path light takes as it bounces from facet to facet? One of the benefits of cutting a diamond by hand is that the cutter analyzes the diamond while it is being cut to determine how the light reflection is really working on that stone. And he makes adjustments as he goes along.


3. Facet size, length, and placement are something that also affect how a diamond will visually perform. The system does not even take these into consideration. Main facets and minor facets can vary in how they are placed and their shape, size and length can vary too. There is nothing in a mathematical formula that can cover this. There are infinite possiblities. Diamonds must be *seen*.


4. Sarin machines are not that accurate in themselves, and readings can vary on the same machine as well as different machines. It is not unlikely to have several different readings from the same sarin and other sarins can have a larger variance. This in and of itself makes it impossible to rely on numbers to give us *visual* results. External measurements do not provide *visual* results.


5. There is no control where the numbers come from. There are no laboratory conditions that would keep the results consistent from one source. Sarins are being provided from numerous sources and will not be consistent. They could even be from different stones for that matter. So this format is not reliable, the numbers could come out of thin air for all they know. So how can visual results be given? They can't.


6. There are many ways to cut a beautiful diamond. Diamonds are not Sony TV's. Light return and beauty are not something that can be predicted soley on numerical formulas. Many diamonds can have different facet arrangements and fall out of the so called "ideal numerical" and produce equivalent or greater light performance than some that are "ideal numerical".


7. Every diamond is individual and the cutters who turn the raw earth into a sparkling gem are individuals themselves. Like artists, they all have a different approach. This is one reason why diamonds are not something where one is identical to the next.


8. The HCA assumes that a diamond is perfectly symmetrical much like a computer rendering. This is not the case with diamonds. All the crown angles and pavilion angles are not identical. They do have variances and are not cut out of a cookie cutter. They are done by hand for the most part.


9. Worth repeating. Paper and numbers cannot give or express the visual or potential visual beauty of a diamond. Most in the industry don't buy sight unseen. There are many stones that can sound great on paper and can just be average in visual performance.


10. It is theoretical and not supported by industry authorities. Much like a drug that was not approved by the FDA. It has many unspoken side effects. It really shouldn't be on the market for consumers to use as some judgement of visual cut quality, or base buying decisions on. There are many things on the web that aren't true, so keep that in mind. Test the facts and see if they hold water. This is mainly for consumers to review so that they can maintain a common sense approach to buying a diamond. There are some on the web that will try to convince you otherwise in their marketing efforts to have some magic bean calculator that will render visual opinions on something it doesn't see. There is no one on the net that can give you results or accurate opinions on how a diamond looks with a few numbers and without *seeing* it. Think about that.

For the last few years, there has been a system that claims to give visual performance of diamonds it never sees based on punching in a few numbers which are then spit back out as supposedly accurate visual results?!

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Megascope is a product of Ogi tech, a competitor of Sarin.


The stated accuracy of both the Ogi and Sarin equipment is 0.02mm when measuring the same stone on the same machine.


You've got a 0.03mm variation but this could easily be accounted for by the use of a different tool that may or may not be callibrated the same. For purposes of deciding on the various ratios use the new one so that all measurements will have been taken with the same machine and at the same time.


If you're questioning whether the two reports are describing the same stones, consult with a professional gemologist.


Neil Beaty


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Thank you both for your answers specialy Jan for your extensive recomendations.


The fact is I am from Europe.

Prices in USA are more reasonable and USD is weak in comparison with EUR.

Since this is the only way to get a diamond from USA, I decided to buy it over the net.


I am aware that there are some risks of not buying the most perfect diamont.

After I did some research about diamonds at the end I found this information about pavilion angle and other external averages. And if there is at least small possibility that diamond will be more brilliant if the proportions are OK then this is one more thing I will check.


I know the proportions are not everything and that diamond can look brilliant even outside 'ideal' proportions but sice I can not see diamonds I am buying, my chances of getting a better diamond increase with more data and statistical informaiton I process. Therefor I asked for sarin reports. No pressure from seller's side I just wanted to see if it comes within recomendations...


I was more concerned about discrepancies of measurments because I have had certain doubt about this sarin reports. But it is about fractures of mm so it can be because of the machines...


Thank you for again, I was a little bit under time pressure but at the end I decided.


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Your welcome. If you really want to know how a diamond will look and you are purchasing over the interenet, there are some vendors out there that can give you more information than just a sarin or OGI. There are some light performance tools and they could take a picture for you too. Check out these links.




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