Can I use the HCA calculator to weed out diamonds?

[nosoup4u]

Good evening all -

I am doing like most here, trying to research and learn as much as possible. Right now, I have been working with Bill Scherlag whom has been of great help. He has found a nice diamond for me, and, I have been just searching Blue Nile as well.

When I enter the diamond that Bill found (the specs) into the HCA calculator on pricescope, I get a score of 2.3 -- or very good.

For about $1500 more (blue nile''s diamond), I get a HCA score of .9.

Can I automatically assume that the .9 diamond will be much better? (assuming everything else is the same, AGS0 certified, clarity is same and color is same). I was thinking of asking Bill to procure the Blue Nile one (since it appears those diamonds are not in-house and can be obtained by him).

In essence, am I using the HCA calculator correctly, taking the diamonds that fit within my criteria (AGS0 certified), and then can I only select ones that would be less than 2 or Excellent across the board using HCA?

The only thing I cannot input is the culet -- most of them say ''pointed'' -- but, I do not know the dimension to enter since I am putting in the crown and pavilion angle. I have just been using .1 as the culet - is this wrong?

Thanks,

James

 

[neatfreak]

HCA is exactly that, a weeding tool. But no tool is perfect, and nothing can beat your eyes if you can get pictures or see them in person and see which one speaks to you. Idealscopes and ASET images are great too. And remember, ANYTHING under 2 is good, so just because a diamond scores below another, if they are both below 2, they are both good. It''s not a selection tool, it''s a REJECTION tool.

 

[Rhino]

Date: 11/6/2007 11:39:13 PM
Author: neatfreak
HCA is exactly that, a weeding tool. But no tool is perfect, and nothing can beat your eyes if you can get pictures or see them in person and see which one speaks to you. Idealscopes and ASET images are great too. And remember, ANYTHING under 2 is good, so just because a diamond scores below another, if they are both below 2, they are both good. It''s not a selection tool, it''s a REJECTION tool.

ANYTHING under 2 is good? I''m not trying to be argumentative but some of the most conservative labs in the world that grade cut would strongly disagree.

Insofar as an accurate tool for rejection, some of the rarest, most precise and most beautiful diamonds in the world score over a 2 including AGS Ideals and very tight GIA Ex''s with superior reflector images.

I''m not knocking the tool and in many instances stones under 2 are just fine but you may want to investigate further what you are presenting as statements of fact before making broad assumptions neat.

Peace,

 

[nosoup4u]

Thanks guys ... I'm not trying to start a debate on which is better. Basically, there are three stones that I really like -- but, unfortunately, would require having Bill send me all three and spending the $200 on the appraisal for each one. Other than the AGS certification, I have no real way of evaluating them from other documenttion - so, I would need to do the evaluation myself. I've already done one evaluation and rejected a diamond; but, this can get quite expensive if I do this. Here are the 2 diamonds from Blue Nile.

http://www.bluenile.com/diamonds_details.asp?__fun_frm=i&track=view_details_btn&elem=img&pid=LD01041602&filter_id=0 -- Excellent (2.375 carats). I-VS2. TIC - .9 (8.64-8.71 x 5.22mm)

http://www.bluenile.com/diamonds_details.asp?__fun_frm=i&track=view_details_btn&elem=img&pid=LD01041601&filter_id=0 < -- 2.236 - 8.47-8.55 x 5.11mm. I-VS2 TIC = 1.1

Bill's diamond he suggested is the cheapest but an I-SI. However, it appears very clean on the table at least (imperfections seem to be around the edges). I am trying to determine which one to have him send me. The one he recommended is the cheapest; but, also, on the pricescope thing, came out as TIC of 2.8. Depth - 61.7%; Table - 57.7%; Crown Angle - 34.6; Pavilion Angle - 41.1. Weight is 2.146, culet is pointed, Dimensions are 8.24-8.27 x 5.10mm; Faceted 1.5%-4.5%. Negligible fluorescence.

All of the stones are AGS0 certified. Price difference between each is about $2K higher as you go up in size.

So, out of these, I am trying to make my determination. Before someone states: bigger is better, the 2 larger stones would require me to use my savings/emergency fund whereas the one Bill sent me does not. I actually am thinking of compromising and going with the middle one; but, the only reason is because Bill's recommended diamond has a higher TIC (using the HCA calculator).

I actually believe his stone is cleaner (even though SI1) because all of the imperfections are not in the table whereas for the other 2 stones above, they appear to have some imperfections; but, both score better on the TIC scale.

Any thoughts among these 3 would be appreciated.

 

[strmrdr]

Table - 57.7%; Crown Angle - 34.6; Pavilion Angle - 41.1
hca is killing the score over the 41.1 pavilion angle.
If the IS image dont show excessive leakage and decent or better optical symmetry its fine.
AGS system must have liked it if they gave it a 0.
The hca is overly harsh on that combo.
Because it cant take everything into account like AGS does and some stones with that average might be an issue it knocks them all down.

 

[stebbo]

Date: 11/6/2007 11:08:39 PM
Author:nosoup4u
Good evening all -

The only thing I cannot input is the culet -- most of them say ''pointed'' -- but, I do not know the dimension to enter since I am putting in the crown and pavilion angle. I have just been using .1 as the culet - is this wrong?

Thanks,

James

It won''t hurt as you''re entering angles. You can just leave it at zero unless the culet starts getting pretty major or you only have %''s.

 

[Regular Guy]

Date: 11/7/2007 12:40:47 AM
Author: strmrdr
Table - 57.7%; Crown Angle - 34.6; Pavilion Angle - 41.1
hca is killing the score over the 41.1 pavilion angle.
If the IS image dont show excessive leakage and decent or better optical symmetry its fine.
AGS system must have liked it if they gave it a 0.
The hca is overly harsh on that combo.
Because it cant take everything into account like AGS does and some stones with that average might be an issue it knocks them all down.

Right.

Without regard to Rhino''s comments...I think that although the HCA for general use is a weeking tool, I think Garry would agree it doesn''t weed effectively among diamonds already scoring 0 for light performance in AGS. Like putting a football through a hoola hoop to test to see if the football is too large. If the football hits the hoola hoop boundary, it''s not because it''s too large...it''s for unintended effective measurment error.

So...you may wish to use something else to weed within the 3 you''re considering, but I don''t think HCA is a helpful tool for this task.

 

[nosoup4u]

Thanks guys -- so, it sounds like I need to just order all three and spend the $600 to have all of them appraised

-

Or, should Bill be able to procure them and then give me his opinion on it? He does not have any of the fancy machines to review it -- so, I have to send it to the appraiser for all of the different criteria.

 

[Ellen]

Date: 11/7/2007 8:30:18 AM
Author: nosoup4u
Thanks guys -- so, it sounds like I need to just order all three and spend the $600 to have all of them appraised

-

Or, should Bill be able to procure them and then give me his opinion on it? He does not have any of the fancy machines to review it -- so, I have to send it to the appraiser for all of the different criteria.

I wouldn't, personally. I'd go with the 2.23 I VS2 and call it a day. Then take it to an independant appraiser if it will ease your mind.

ETA And at VS2, the inclusions shouldn't be a problem.