It is a highly subjective opinion in a single number for easy digestion.
Among all the vile gimmicks designed to promote proprietary standards in diamond grading, nothing is more sinister than the infamous HCA calculator.
A close cousin of the Magic 8 Ball, this is a marketing tool that is supposed to calculate a round diamond grade based on just a few parameters.
HCA calculator is the online tool invented by Russian hacker-turned-diamond-specialist.
Octonus Software Co and the Australian-based self-proclaimed diamond guru Garry Ian Holloway, the holder of the US patent number 7,251,619.
While Louvre and Hermitage are still waiting for Gary to come up with an app that decides which DaVinci should be displayed and which tossed into a dumpster, Mr. Holloway is busy putting a stamp of approval or disapproval on diamonds he never sees.
The "calculator" is loosely based on diamond charts created by GIA to determine the cut grade of a round brilliant.
The main goal of the "calculator" is to steer clients to the small group of dealers and their paid trolls who turned what used to be the unbiased consumer forum Pricescope into their personal leads-scavenging grounds. Currently every score is accompanied with a list of "suggested" diamonds available from Halloway cronies on Pricescope. Needless to say he gets a cut of every listing
You get three HCA scores for free, if you need more a payment is required. Using a proxy server (VPN) will protect you from wasting your money, as well as keep your private information out of Putin's intelligence hands.
What you need to know about HCA calculator is that it is:
The HCA is an obscure and deceitful marketing tool often used by fake "diamond specialists" crawling the web in search of their next “pay-per-referral" scheme victim.
The HCA is highly subjective and misleading calculation because its score is based on arbitrarily picked preferences having nothing to do with the diamond’s actual appearance or its beauty.
HCA works by calculating a score on a scale from 0 to 10, with 1.0 being the best. Anything higher or lower is deemed less desirable.
The HCA calculator compares the diamond's depth, table, crown and pavilion angles. But in reality, the result is determined mainly by the pavilion angle. The other parameters are used in order to obscure this simple fact and to make the unsuspecting consumer think that there is more to it.
In fact, if you choose a GIA stone with an excellent cut grade and pavilion angle 40.5 to 41 degree you are practically assured to pick a stone with a "good" HCA score.
Just in case the result is dished out along with a disclaimer rendering it completely meaningless, in case of any scrutiny.
Jewelry professionals do not use HCA and are completely oblivious to the fact that it even exists.
Using numbers to evaluate the diamond beauty is as dumb as deciding a beauty pageant without seeing the contestants, by simply comparing their hip's measurements.
In order to get an HCA score of a diamond, you need to copy values from the diamond report, such as total depth, table, crown depth or angle, pavilion depth or angle, and the culet size.
The results are displayed in a form with a score, the lowest being the best. There is no explanation on how such whimsical properties as fire or scintillation could possibly be quantified (let’s leave this mystery unsolved for a now). There is also a “factor” called “Spread”. The difference in diameter between a “Good” and “Very Good” spread on a one carat stone is a meager 0.1 mm - the thickness of a sheet of a paper.
Looking at the chart above, one might be thrilled to find an extremely rare stone. Oops, here is the same stone with a 60% table. Same excellent grade across the board. The psychedelic chart on the right changed its shape (what is it? what voodoo science does it represent?) to leave no doubt in our mind that behind the scene some important calculations were actually performed.
Let’s look at a stone with a significantly lower score but fairly reasonable proportions
Now we changed the crown angle to an extremely steep 40° and depth to a ridiculous 66%. The score increased to 4.3 from a low 5.3!!!!!!! What the @#$% ? The 40.5-degree pavilion angle improves the score even when the rest of the metrics are way out of normal range.
The original disclaimer displayed with every result was later removed, it stated : “Even though HCA grades cut more effectively than systems like the AGS, it does not yet factor in symmetry and minor facets. Having found a diamond that scores well, you should employ an expert appraiser to examine the stone. If you decide not to, then at least compare the diamond to others and/or view it through an ideal-scope.”
Translation: “Congratulations! You just performed the incomprehensible task of calculating a meaningless number. In case anyone questions it, you are on your own. Now that you are confused and disoriented, we expect you to buy from us because we are the only ones to possess the secret knowledge of what that number actually stands for.”
The HCA calculation doesn’t take into account factors such as symmetry or minor facet variation. The calculation is based on arbitrarily decided preferred parameters and any deviation will be punished by a poor score with complete disregard to overall proportions and appearance.
HCA is a lobotomized version of a GIA evaluation calculator that is available only to trade members. The GIA score does account for symmetry, polish, and minor facet data. And what’s more important, the GIA score is not presented as a verdict but as a mere advisory.
The last point to make - all diamonds are three-dimensional objects observed at many different angles, not just face down. Light interaction with any faceted gemstone could be fully assessed only by an experienced person such as jewelry professional by examining the stone movement in natural light without the use of magnification.
The verdict - if you want to assure a good HCA score, simply keep the pavilion angle at or below 41 degrees and don’t waste your time crunching meaningless numbers.