HCA - Question

[Anthonyd]

Just curious as to what makes the HCA accurate? Is it a proven thing or theory? If it is a proven fact, wouldn''t the cert labs be using it? Is it strictly theory at this point in time?

Don''t flame me, I''m just asking.

 

[oldminer]

The HCA works. It is something that is very useful, but the major labs generally cater to their best customers which happen to be diamond dealers. Do you think diamond dealers like having such a grade unless their stone graded near the top? No way. Too many diamonds are ordinary, not superior.




That's why the HCA is out here, with the public. It is not going to be something the average diamond trade embraces, but it is very helpful in judging diamonds that you cannot see in person....

 

[Anthonyd]

Is it possible that a diamond scores poorly on HCA yet "outperforms" in real life a stone that scored high on HCA?

I just think that people rely on this too much. For example I compared two stones last week, one that scored well on HCA and one that scored poorly. The one that scored poorly was D in color the other was G. In my opinion the D (which scored worse) performed better.

Just my 2 cents.

 

[Blueman33]

I think the HCA is great.

However, I did have a very well known vendor ask me, "Which is better, a diamond with an HCA of .8 or 1.8?" Well, obviously you know my answer...".8".

"No, he stated, 1.8 is better..." and went on to give his theory of some bias in the HCA program that yada yada yada (meaning I forgot the exact argument).

Just goes to show, everyone has an opinion.

 

[Garry H (Cut Nut)]

yup - everyone can have their own opinion.

HCA is for rejection to narrow down selection - and in my case is confirmed by ideal-scope.

if i have the stone in front of me i do not waste my time with hCA - just use the ideal-scope.

But it is possible that some people - especially young people with 21/21 eyesight - will not like the shallow stones that get the lowest score because they get less spread penalty.
the yada yada guy has a point

 

[Paul-Antwerp]

Indeed, people rely on it too much. It is a tool not to be used on its own. Its use is in weeding out the bad ones, not in selecting "the one".

To your straight question: is it possible for a good stone to get a bad score? The answer is no.

On the other hand, is it possible for a bad stone to get a good score? The answer is yes (that is why the stone should be checked and verified).

Therefore, it is possible that a better score looks worse than a slightly less-scoring stone. That is not a problem: the HCA tells you how good a specific stone "possibly" can be, based upon limited information.

The detractors of the HCA always argue that it does not work because they say a good stone can get a bad score. That is untrue. It is the other way around, and that is basically not a problem, since one should always use the HCA as an elimination tool to weed out the definite bad performers.

Live long,