Very good cut, just outside border on bottom left of HCA chart

[vtx531]

Trying to pick out a good one. Seems like I should look for one with a depth less than 60% so I can have a good spread. Is this OK as long as the angles are correct for it? Any reason not to focus on lower depths so long as the HCA score is ok?

Why is the excellent/ideal cut box area in the upper right instead of more centered in the red portion of the HCA chart? I have found a diamond that scores just barely to the bottom left of the excellent range and the diamond is rated as very good. Can a very good cut diamond ever look better than an excellent cut? Should I stick with something in the excellent box?

.84
G
SI1
VG cut
depth 59.2%
table 57%
thin-medium faceted girdle (how important is is that the girdle is faceted? are most? should I narrow search to thin to maximize spread?)
polish VG
sym EX
FL none

scores excellent on all the hca factors and 0.5

the girl who this is for has dark hair and light skin

I guess my question is should I ignore this type of diamond or is it ok to look further? Seems like this type of thing would be good because it should look better and be cheaper?

Thanks -Chris

 

[Lorelei]

Date: 9/30/2009 3:52:31 PM
Author:vtx531
Trying to pick out a good one. Seems like I should look for one with a depth less than 60% so I can have a good spread. Is this OK as long as the angles are correct for it? Any reason not to focus on lower depths so long as the HCA score is ok?

Why is the excellent/ideal cut box area in the upper right instead of more centered in the red portion of the HCA chart? I have found a diamond that scores just barely to the bottom left of the excellent range and the diamond is rated as very good. Can a very good cut diamond ever look better than an excellent cut? Should I stick with something in the excellent box?

.84
G
SI1
VG cut
depth 59.2%
table 57%
thin-medium faceted girdle (how important is is that the girdle is faceted? are most? should I narrow search to thin to maximize spread?)
polish VG
sym EX
FL none

scores excellent on all the hca factors and 0.5

the girl who this is for has dark hair and light skin

I guess my question is should I ignore this type of diamond or is it ok to look further? Seems like this type of thing would be good because it should look better and be cheaper?

Thanks -Chris

Hi Chris and welcome!

Firstly with the depth a good range is 60 - 62% to get a good spread, go too shallow and sometimes cut quality can suffer and you can get issues such as obstruction ( visible darkening at close scrutiny due to the viewer's head or body blocking light to the stone) if the crown and pavilion angles are also shallow ( what we call a shallow/ shallow), often these stones are better suited for pendants rather than rings.

However you can find some great diamonds which are a little more shallow, I would look at some diamonds which have no less than 59% for depth, crown and pavilion angles of around 34- 35 degrees and 40.6 - 41 deg respectively ( and get images if possible to check the stone out properly) and a table of around 56- 60%. You might be able to find what is called a 60 60 type diamond which could suit you if the angles as above are within good range.

As to the HCA, it is used for rejection not selection so use it as a first round elimination tool to collate the diamonds which score below 2, then evaluate with Idealscope or ASET images as the next stage. This is by far the best way to judge any diamond rather than rely on the HCA to choose a diamond.

This page explains in detail the usage of the HCA.

Concerning the cut grades such as GIA Excellent and Very Good as usual images are very useful, some Excellent cut grade diamonds can have what we call steep deep angles and show leakage, further clouding the issue is the fact that GIA round the angles which make images of " borderline" angle combos even more essential. Although the term Very Good implies a diamond might be of lesser cut quality than an Excellent ( referring to GIA cut grades) this isn't always the case, some GIA VG's can be beautiful so again images come into play to help judge the cut properly.

Concerning the diamond you listed, more info is needed such as the crown and pavilion angles you entered into the HCA plus-

the diameter in MM
star and lower girdle facets

With the HCA score for this stone, it suggests it is on the shallow side and might suffer from obstruction ( as explained above with visible darkening of the diamond when viewed closely) so if this diamond is being sold online then an Idealscope image would certainly be helpful if you can get one.

Girdles - faceted is fine, read morehere for more information on girdles.

 

[stone-cold11]

Ya, show us the numbers you use to get the HCA score.

Better yet, the grading report.

 

[vtx531]

Oh geeze. I dunno how I forgot the other important stuff. Here:

6.16 x 6.20 x 3.66

p= 40.4%
c= 34.0%

What are star and lower girdle facets?

 

[stone-cold11]

Do you have the report number?

On GIA report.
The star number will be the top left number, just beside the table number, usually 45%-55%.

The lower girdle facet number will be bottom left number, beside the culet, usually 75%-85%.

 

[vtx531]

Certificate No: 2101620647

I typed it in google and there are many websites that have this same diamond for sale. exceldiamonds.com says you can see it in their showroom in NYC and they can provide photos and idealscope on request. Maybe I will have to take a trip to NYC and check it out.

 

[stone-cold11]

Yap, that will be safer.

 

[Lorelei]

Date: 9/30/2009 6:31:12 PM
Author: vtx531
Certificate No: 2101620647

I typed it in google and there are many websites that have this same diamond for sale. exceldiamonds.com says you can see it in their showroom in NYC and they can provide photos and idealscope on request. Maybe I will have to take a trip to NYC and check it out.

If you can that would be great.

This link shows you where the star and lower girdle facets are on a diamond and explains how the LGF's work.