HCA crib notes

[johngalt2004]

I''m going to have to look at some ags 0''s blind to the HCA tool, so I made some crib notes to take along.

Could someone let me know if this is "essentially" correct as far as a pocket version of the basics (at 62 depth and 55/56 table):

40.5 - 40.9 pavilion angle is ok with virtually any crown angle <35. Perfect dead on sweet spot is 40.75 + 34.5

41 PA is ok with crown angle < 34.6
41 PA might be exceptional with CA 32-34

41.1 PA not likely to be exceptional, but can be ok with CA <33.7

Add .1 to crown min for 61 depth
Add .2 to crown min for 60 depth

Subtract .2 from crown min for 63 depth
Subtract .2 from crown min for 57 table


Will this see me safely through and avoid any after sale "HCA shock"?

 

[Regular Guy]

Apparently they used slide rules in the original space program, too.



Not sure what the deal is.

Regardless of your relationship with this guy, it''s known you don''t have to accept whatever he shows you. You can use whatever criteria you want, right?

Be somewhere, where you can turn on a computer.

A print out of the HCA eval is in my appraisal of my stone. I do note, however, that sometime after my appraisal was done, the woman who actually did it was no longer part of that practice''s office.

It''s not such a radical thing, really.

Has anyone done this, live. Just brought it up while shopping? Why or why not.

 

[strmrdr]

few adjustments:
first good arrows? (hca works better with symmetrical stones)
55/56 table

Then: 40.7-40.9 with 34-35

Then 41 > 34.5C

Then 41.1 > 34.3C

Then 41.2 > 34C

Then 40.4-40.5 > 35.5C except in a tight stone 40.5/34.5 can rock.

40.6 is a wild card can go either way better with steeper crowns or shallower depending on whats in the average.

Or Buy an ideal-scope or ASET and do it right :}

 

[hearts-arrows_girl]

Date: 9/21/2007 3:00:52 PM
Author: Regular Guy

Has anyone done this, live. Just brought it up while shopping? Why or why not.

I did exactly that. I had a very good relationship with my sales lady and had her go to the PS site and run the numbers through the HCA. She had never seen this tool, and bookmarked it on her computer to use in the future. Most jewelers have internet because they need to see what stones they can pull in for you to look at.
I also would have her Xerox off the grading reports for each stone I was considering and I would write at the top of the paper the price and any personal thoughts I had about each stone, then go home and look them over further. I found it is always good to "sleep on it" when deciding. That way you don''t let sales pressure or the exitement of the moment sway your judgement.

 

[johngalt2004]

Well I bought my stone knowing it had a bad HCA because I had memorized the basic idea. So I did not want for the computer at the scene...

What can I say... I think it is totally mind-blowing. I compared it to an option that had a 1.1 HCA. I could not differentiate between them in any meaningful way honestly. The 1.1 HCA diamond was .1 smaller and $500 more. The third option had unknown angles, but was $400 more than this one and the same size. Had prospects of most likely returning a better HCA but I could not see that it was a better looking diamond in any respect. Neither could a passerby - who agreed no way would she pay $400 more for one stone than the other, no matter which was which (they looked the same).

It is a real odd-ball though.... very odd in that I guess this would not make the old AGS zero because the table is very big and the crown angle is very big. It is a freak! I should not have bought it based on what I have read on here but I did buy it.

In spite of very odd specs, it has ags performance based zero paper and it looks mindblowing really. I could not wish it was more beautiful than it in fact is. I''m just going to have to take my humble medicine that I did not do "as well as possible" on my little diamond hunt though because I know I could have had this stone cheaper on line (although I would have been doing a lot of hunting/pecking to find this super clean SI2). But I am going to shake it off and hope my wife likes it (she has had a .64 IGI ideal for 10 years so she should be impressed).

So here''s the specs on the little bastard that has no business being an AGS 0, but is one:

57.7 table
61.1 depth
41.2 pav angle
33.6 crown angle
1.19 ct
SI2 super eye clean with white inclusion coverable by a prong - I could not find the inclusion without specific direction on where it was
H
$6100

poor HCA score of 2.6 but gorgeous diamond. and my wife and her friends will never ever ever know that it does not have an HCA below 2 (if I can discipline myself to drop it from my mind and not brood about it)

There are people with worse problems than having this stone I''m sure!

Thanks everybody on PS - I learned so much and I wish I had come sooner.

Everyone has different values and pain thresholds and priorities. For me, getting this stone was a very happy ending to this whole thing. ags cert date is the same as my birthday, so God wanted me to buy this stone and get on with life I think

Now I just wonder how the hell this stone got a zero!?? turns everything on its head.

oh well, thanks again.

By the way, I wonder if there is anyone, anywhere, outside this board, who would look at it say: "nice stone but it looks like the pavilion angle is .1 too steep for a 1.9 HCA score".

 

[Garry H (Cut Nut)]

I have no problem with

Date: 9/21/2007 5:47:43 PM
Author: johngalt2004


57.7 table
61.1 depth
41.2 pav angle
33.6 crown angle
1.19 ct

poor HCA score of 2.6 but gorgeous diamond. and my wife and her friends will never ever ever know that it does not have an HCA below 2 (if I can discipline myself to drop it from my mind and not brood about it)

I have said that the HCA scores for symmetrical stones can allow some slack, and I know that HCA was worked out for one eye - when we look with 2 we see less table leakage.
also if your stone is very slightly painted then it would effectively be a little shallower.

 

[johngalt2004]

God bless you Garry you are a great man in my book for posting this, a real gentleman.

You have no idea how a positive word from the HCA inventor puts my mind at ease and will give me the freedom to really enjoy what was for us a big ticket purchase for a very special occasion. No idea.

I actually kind of enjoy the notion that some craftsman tweaked this into the ags zero cherry zone with his experience and skill. Good for him and good for me... a win-win

Thank you.

 

[Garry H (Cut Nut)]

Date: 9/21/2007 8:47:19 PM
Author: johngalt2004
God bless you Garry you are a great man in my book for posting this, a real gentleman.

You have no idea how a positive word from the HCA inventor puts my mind at ease and will give me the freedom to really enjoy what was for us a big ticket purchase for a very special occasion. No idea.

I actually kind of enjoy the notion that some craftsman tweaked this into the ags zero cherry zone with his experience and skill. Good for him and good for me... a win-win

Thank you.

You are welcome
This slide attempts to show the stereo vision reduction in leakage dead spots.
When seen from a tilted side view from each of our eyes perspective our brain will process and will see brightness over dull spots. So one eye will see a sparkle and the other may see a dull patch on the same zone - the out come is sparkle - paper, scissors rock

 

[diamondseeker2006]

Please do relax knowing you got the top cut AGS will grade! Where we really need the HCA is to help us with GIA excellent stones because some are better than others. But I don''t even put the numbers of an AGS0 in there. It''s already proven it is an excellent performer if it got that grade!