Using The Holloway Cut Advisor (HCA) Tool

Q:

Hi Liz,

First of all, thank you so much for this blog. I searched the internet for so long but this is by far the most informative and helpful site I found!!

I have been searching for double and triple halo engagement rings and finally found one that I love: http://www.zoara.com/engagement/rings/p_triple_halo_diamond_ring#p=170561

Now I just need to find a diamond. I’m looking for a 1.00ct (or bigger) with G+ color and VS1 or better clarity. My budget is $8K for the diamond. I found this diamond: 1.02ct F VVS2. The HCA score is 1.9. What do you think?

Thank you so much for your help Liz. I really appreciate it.

Michelle

A:

Hi Michelle,

I think your setting is lovely – very unique. I do not recommend that 1.02ct F VVS2.

The HCA is a computer algorithm that serves as an elimination tool. It is generally used when you don’t have anything other than a generic lab report’s proportions like this: 

However, what most people do not realize is that the crown and pavilion angles reported on a GIA report are averages. GIA averages all eight crown angles and are reported to the nearest half of a degree (0.5°). Additionally, all eight pavilion angles are averaged and reported to the nearest multiple of 0.2° (e.g., 41.0°, 41.4°).

• Crown Angle = the angle of the bezel facet plane relative to the table plane
• Pavilion Angle = the angle of the pavilion main facet plane relative to the table plane

If you were to see view all angles on a round brilliant diamond, the plot diagram would look more like this:

An example of different angle values for the 8 crown and 8 pavilion facets.

Therefore, the diamond that scored a 1.9 isn’t recommended due to the dark area under the table indicating light leakage. If you read my article on diamond cut, you’d know that the angle between the pavilion facets and the girdle is the most important as this controls the production of brilliance by reflecting rays of light from the back facets. Your original 1.02ct F VVS2 has misaligned facets that miss the opportunity to reflect light. It’s not a terrible diamond, but you can find better for your available budget.

HCA Score 1.9 with corresponding image of diamond.

Therefore, we can see that although the HCA tool does a decent job of ‘predicting’ light performance, it should in no way be used as a final evaluation tool. Use it only as a guide and leave your final decision to viewing actual diamond images and if available ASET, ideal-scope, and HD videos.

As for your diamond I recommend this 1.04ct G VVS1 for $8,490.00.

Let me know what you think. 🙂

Kind Regards,

Liz

Q:

Thank you so much Liz.

It seems like I will go with this diamond. You really relieved a lot of stress that I may have experienced if I was to do this all alone. Thank you and have a great weekend.

Regards,

Michelle