HCA, light return, and much confusion

[PoopEater]

I was browsing the diamonds over at goodoldgold.com, and came across this guy.

http://www.goodoldgold.com/aaa5t_g_vs2.htm

It comes up with a score of 0.4 on the HCA, which I would think would place it very highly in the realm of purty diamonds. When looking at the diamond sim (very last image on that page), it gets only a 'medium' in white light return and only 'high' in scintillation.

The diamond located here:

http://www.goodoldgold.com/aaa7t_e_vs2_h&a.htm

Comes up with a 1.1 HCA score, which I would think is 'worse' than the 0.55ct stone linked at the top of this msg. Yet, the simulation on the bottom of the page of the 0.72ct diamond shows 'very high' white light return and higher scores in the other two. The simulation also looks much more breathtaking on this 0.72ct than on the 0.55ct linked at the top. How can the larger stone, with a poorer HCA score, give so much better light return than the technically superior smaller stone?

 

[Garry H (Cut Nut)]

The Brillianscope has set light positions.
I guess this is one of those stones that lights up in between the set light positions.

 

[Garry H (Cut Nut)]

These pictures are from the website with Jonathons version of an idealscope.
Assuming the images are shot consistantly you would expect similar light return, with slightly more coming from the one on the left which scores .7 on hCA. The one on the right is the 1.1 HCA stone.

What do you think?

 

[mrmarius]

This tells me that numbers and HCA scores and Brillancescope scores are great, but there is no substitute for looking at the stone through an ideal-scope.

 

[Garry H (Cut Nut)]

M do you think there is a problem with the HCA scores based on the two images here (or on GoG site)?

 

[Emrldforher]

I find the differences in brilliancescope reports very interesting. Bottom line, as both diamonds score less than 2 on the HCA, you would expect them to both have very good light return and perform very well overall. I find it really interesting that the .55ct stone "only" scores a medium in white light return. Based on my understanding that the scores are compared to a huge database of diamonds, I would expect that a medium should mean that in general its not a very good performer in that category.

What I find more interesting is that the lightscope image of the .55ct looks very good. It should perform well based on the image. The b'scope performance indicates that it is a fiery diamond with strong scintillation, but lacking in white light return. That doesn't seem to be supported by the lightscope image.

The only thing I saw in the lightscope report of the .72ct diamond that seemed noticeably different than the .55ct is in the center of the diamond, there appears to be a good deal more pink "shafts" in between the arrows, whereas the .55ct diamond seems to be more of a deep red. It isn't as noticeable in the two images Garry posted here as they are small, but if you look at the larger images on the individual pages you will see what I'm saying. I would think the pink would represent some light leakage.

Bottom line, this type of result is what makes me question the brilliancescope results. As the lightscope reports seem so similar, I have a hard time understanding how one could have medium light return and the other very high. I'm so curious that I'm tempted to call Jonathan and ask him what his eyes tell him when looking at both of these diamonds together!

E

 

[Garry H (Cut Nut)]

E I agree with you that there is some partial leakage in the deeper .72 ct stone. That is what I meant when I asked would you not accept that the .55ct has a better idealscope image.

You could expect a little less light return from the smaller stone however because the star shafts are fatter (= shorter lower pavilion facets and?smaller table?) which also gives a little more fire (it is a nice trade off and one reason why I do not get too carried away with GIA and Rocdoc claiming the secret facets have a big impact).

Finally (its late here) Jonathon purchased this .55ct stone because it is a great stone. looks like the BS might have shot him in the foot?

And last of all - you may notice the H&A's stars in the shallow stone are dark = Jonathon uses a h&A's viewer with a bigger hole than some (about 18 degree).

 

[Emrldforher]

Garry,

Based on the HCA, lightscope and b'scope results, the HCA and lightscope seem to support each other. Remember the old Sesame Street (did you get that in Aussieland as a kid?) skit, which one of these pictures doesn't belong.....

By the way, I'm not trying to bash the b'scope. I think all of these tools are great to help narrow down the diamond search process. Certainly when you have several tools telling you similar things about a diamond, it helps in your selection process. However, when they have differing results, it has the effect of confusing us consumers!

E

 

[mrmarius]

no I don't CutNut, I was more speaking in general terms. The stones in the pictures look like they should based on the scores. My personal preference is to have all the data, which includes both HCA scores and what my eyes tell me.

 

[PoopEater]

Thanks for the great discussion, everyone. The BS results are definitely odd. Do you think there is any chance that Jonathan posted the wrong BS analysis for this stone? I noticed that the ID numbers are very similar, but don't match exactly (the BS has some extra digits). The HCA and IdealScope performance both lead me to believe that this is a better stone than the BS indicates.