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The HCA score measures the amount of light entering the diamond through the crown facets,  then internally reflecting within the facets of the pavilion and then exiting  through the crown facets.  You want the maximum amount of light to exit through the crown facets as that is what the eye will see.  There are four basic factors that influences the light  entering the crown facets and then ‘leaking’ out the pavilion facets where the light is not seen.  The idea is to cut the diamond so that the light will internally reflect within the diamond and the light then exits at the crown facets where it will be seen when observing the diamond.   The four factors that affect the light internally reflecting within the diamond and then  consequently out the crown facets are as follows:  the crown angle,  the pavilion angle,   the table percentage, and the depth percentage.

At USA Certed Diamonds I constantly inspect diamonds with HCA readings that I order for clients that have HCA scores of 2.4 or less and am never disappointed with the overall light return, fire, and scintillation.    Also, I have seen many, many diamonds with HCA scores less than one and these diamonds have absolutely amazing brilliance, fire and light return.

At USA Certed Diamonds all round brilliant cut diamonds are now chosen based on the HCA score being in the top excellent category up to 1.9 or in the Very Good category from 2 to 2.4.

As well, I place a lot of importance on the spread and proportions of the diamond.   I try to keep the depths less than 62% and the tables from 54 to 58%.   A lot of effort goes into choosing the right diamond for you so that everything is balanced with the lowest possible price.

Please note that as a rule the HCA score less than 2.4  will usually mean a very high brilliance.   However,  there are diamonds with HCA scores above 2.4 that have amazing brilliance as well.  Once I’ve chosen the right diamond for you with every factor in your favor I have an independent expert in NYC who will further check the diamond to make sure that it has the brilliance that matches the excellent HCA score.  An ‘idealscope’ photo of the diamond can be taken as well.  However, I’ve rarely ever seen a diamond with an excellent HCA score that would not do well on the ‘idealscope’.

To summarize:  the HCA is an amazing tool for determining brilliance and is an integral part of the selection process when locating a modern round brilliant cut diamond for you.