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Table/depth %


chan2402002
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hi all.

 

how is the table and depth percentage calculated? i assume is basic math based on the measurements of the diamond.

 

i have a EGL-USA cert and then i had the stone appraised by an independent appraiser. the table and depth %'s do not match up between the two.

EGL-USA cert has one measurement and my appraiser has another.

the appraiser measured the stone diameter/height and it matches the cert spot on.

 

just out of sheer curiousity, if the diameter/height measeurements are identical between the egl-usa cert and the appraiser, shouldnt the table/depth % be also?

Edited by chan2402002
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Assuming that the stone is round, table % is the average table diameter divided by the average girdle diameter.

Depth % is the depth divided by the average of the minimum and maximum diameters.

 

Depth% can be calculated using the dimensions provided on the EGL-USA report and yes, they should match. It’s probably a simple math error by the appraiser. The table measurements don’t appear on any of the EGL-USA documents I’ve seen so the difference may have to do with different measurements. Call your appraiser and ask them.

 

Neil

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I think it's also important to note that measurements will vary from one gauge to the next.

This will account for a small difference in depth percentage-- for this reason it's likely that the depth percentage number would be slightly different from an appraiser measuring the diamond as compared to an EGL report.

 

table measurements are more approximate than that--- so variance there is expected.

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gauge.JPG

here's the one we use Neil.. I used to have the "deluxe" digital model, but it proved to be less accurate than this mechanical one.when you use this one you need to estimate the second decimal place, but we find the results are more consistent than the digital gauge.

 

Since GIA publishes measurements to the second decimal place (5.00), we like to also measure our diamonds to the second decimal place.

But we have found that GIA's numbers rarely are the same as ours (to the second decimal place)

it's also been my experience, on diamonds that had both GIA as well as EGL reports, that the second decimal place differed between those two labs as well.

I think it just has to do with the tolerances of the tools.

Edited by diamondsbylauren
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the appraiser measured the stone diameter/height and it matches the cert spot on.

 

David,

 

I understand. I think we're answering different questions. There are only 3 variables that go into the depth calculation. If those 3 measurements are 'spot on', which I take to mean identical, then the results should be identical.

 

Neil

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