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Halloway Cut Adviser


pfq1982
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What's the general opinion about using this to identify good light performance diamonds? Mostly accurate, generally accurate, doesn't filter out some stinkers, etc.? I'm wondering if it would be a good filter to buy online or if you have the adverse selection problem of people selling a lot of duds that yield a 1-2 score on Halloway online because people like me might buy them just for supposed light performance?

 

I'm looking for opinons of people that have experience looking at diamonds and comparing to how they score on HCA.

 

Also... any truth to the statement that stones scoring < 1 tend to not be as attractive as stones scoring in 1-2 range?

 

Please don't tell me I'm an idiot for using this, that I need to use own eyes, etc. I wrote down the angles on GIA reports for a couple stones that really sparkled in stores and they were all 1.3 - 2.8 on HCA. This before I knew what HCA was. But I want to pay online prices so wondering if I am LIKELY to get one of those top sparklers I noticed in the stores if I find a stone online that scores well on HCA.

 

Thanks a ton. This might be my last post!

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Personal opinion. Help yourself at the salt bucket before reading.

 

The HCA is a reasonable filter, and it's better than looking at table and depth %, but:

 

1. It reflects Garry Holloway's personal preferences rather than yours

2. It yields false positives and false negatives for reason 1. above and because (like anyone here, including myself, that dares comment on a stone on the basis of 4 numbers) it makes quite a few assumptions about the rest of the stone (perfect simmetry, medium girdle, no brillianteering, ...)

3. It's meant to act as a reject tool, not a pick tool. Using the HCA to say "although both these stones score below 2, but this stone scores higher than that one, therefore it's better" is a completely inappropriate use (according to Garry). And that's before we consider points 1 and 2 above

 

Re: you preferring ranges that score higher - see point 1 above. The scoring on the HCA reflects partly the laws of optics, and partly Garry Holloway's taste and experience. Stones that score very low will tend to have (subject to the usual assumptions) a very high % of reflected light, but probably not as much sparkle or fire.

 

I think you are likely to get a good score on the HCA if the stone is lively and performs well; the reverse is also true but you know the ultimate test, and you are behaving very sensibly by looking at the diamonds and forming your own judgment and taste.

 

Good luck!

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Garry Holloway makes it very clear that the HCA is to be used to weed out poor to mediocre diamonds, not to be used as a picking tool. This makes sense as the HCA measures only 17 of the 58 facets that comprise the round brilliant shape.

 

The other 41 facets, especially the upper and lower girdle facets; their facet angle and size critically impact optical light performance which you can not ascertain or determine from the lab grading report. HCA scores of 0-2 might be a good starting point but certainly if you're shopping on-line additional evaluations of light performance should be obtained by you from the Vendor.

 

We have seen diamonds that score in the mid 2's on the HCA face up better with more zing compared to diamonds with HCA scores below 2.

 

Another point for you to consider is that two diamonds with identical HCA scores may visually differ on brilliance, dispersion, and sparkle because the facets not measured by the HCA have been cut differently. It does not make one diamond better than the other because beauty is a personal preference, but it certainly indicates that you either need to physically see and compare the diamonds for yourself or work with a vendor that can eyeball them for you and clearly describe differences and nuances between the diamonds.

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Garry Holloway makes it very clear that the HCA is to be used to weed out poor to mediocre diamonds, not to be used as a picking tool. This makes sense as the HCA measures only 17 of the 58 facets that comprise the round brilliant shape.

[snip]

If one wants to be really hypercritical, it takes into account none, since all the measurements input to the HCA are averages (including table and culet)... :huh:

 

Oh, and pfq1982 - what do you mean your last post? You are NOT leaving here without telling us what you picked in the end!

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Haha, fair enough! Thanks to you all I feel I am well-equipped enough to make a decision (and dig my own grave...).

 

I bought a 1.45 ct, RBC, GIA rated, F VS2, Exc/VG/Exc, 7.30 - 7.35, 57 table, 60.5 depth, 34.0 crown, 40.6 pav on BN for $10.9k. Haven't seen it yet, but I'm keen to compare to other stones.

 

Of course buying through BN leaves me stranded on the setting so that's my next quest. I LOVE the Cartier Ballerine set w/ a round in platinum, but Cartier doesn't sell separate settings. So I need to find someone who's a good copycat. The ring looked so good in Cartier I almost shelled out for the whole thing (1.11 Exc/exc/exc H VVs2) but thought I could do better on the stone and find that master copycat somehow, but I'm worried my setting won't have the same shine as the Cartier

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  • 8 months later...

I'm back with another question re: wedding rings (another topic), but first I wanted to update my engagement ring experience for everyone who assisted me on these boards (David, Neil, Lauren, Jan, Barry, and sorry if I missed anyone else)... I bought 3 stones from BN that scored well on the HCA (~2) without having some of the more unusual proportions that qualify for top scores. Of course the visual performance is key so I took them all to work and had the ladies do a blind visual preference test... interestingly nearly all preferred the same stone, and it wasn't the one I posted above. (For anybody that is very familiar with HCA, one of the stones scored as a BIC and to my eye returned the most light but is was very white light (more flashes than sparkles) and I think the ladies shied away from it in favor of the more colorful and scintillating one) I returned the one above and bought this stone:

 

1.46 ct RBC, F SI1, GIA rated, EXC cut, EXC polish, VG summetry, no fluor, 56% table, 61.7% depth, 35.0 crown, 40.8 pav, thin-slightly thick faceted girdle.... 7.27 - 7.31 x 4.50mm for $8124. I think I got a good price (you guys tell me!) probably in party b/c the stone is admittedly not eye-clean from the side (can see black spot inside). Can't notice from the top. But for me the brilliance and sparkliness were what mattered most.

 

I think the hours of sweat and research really panned out, as my girlfriend has gotten tons of compliments about how sparkly the stone is (it definitely ain't the biggest in her office!), so thanks again for everyone here that helped get me up the learning curve.

 

BTW if anybody wants to duplicate my experience... BN wouldn't let me buy more than 2 at a time within the 30 day return window so I had to use family to purchase the other and mail it to me. And walking around with 30k+ worth of loose diamonds on me in NYC was nerve wracking! Also be very careful taking your preference survey b/c the wire prong that BN ships the diamonds in is very unstable.

 

P.S. Purchased the setting in the diamond district. Unique setting that flatters the diamond but the side stones are obviously not as good as this stone upon close inspection. Having spent a lot of time browsing in the diamond district, subpar stones in settings and wedding bands are an occasional problem. (was actually there today looking at wedding rings and a diamond FELL OUT AS WE WERE LOOKING AT THE RING.. though to be fair it allowed us to put it aganist white paper and it was clearly an F / colorless stone)

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Hey - good to hear from you! It sounds like you got yourself (or herself) a really nice stone at a reasonable price. As long as the stone is set well (possibly with a claw/prong "hiding" the side view of the inclusion), no-one is ever going to notice.

 

Your observation on the HCA/BIC stone is interesting. GIA and AGS (and Tolkowski before them) have identified three parameters to define how a diamond behaves; brilliance (the total amount of light returned) is one, but contrast (sparkliness) and refraction (fire) are the other two. In general people prefer stones that are balanced in showing all three characteristics. BIC stones are (if the HCA works) more brilliant to the expense of showing less fire and contrast...

 

Having said that, I'm not sure that was the question, so I'll shut up.

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