Low HCA Scores and "shallow shallow" ideals

[derekinla]

For the experts (Garry, Rhino, Rich, Dave). Is it true that stones with low HCA scores ("shallow shallow" AGS 000''s with say HCA''s of 0.3-0.5) tend to lack contrast? If this is true, I assume they tend to have more whitelight return? Can somone post some pics of stones with different HCA scores (i.e. 0.3, 1.5, 2.0) side by side?

 

[Garry H (Cut Nut)]

http://www.ideal-scope.com/idealscope_reference_chart.asp
check this out Derek.

Remeber that the closeness and sixe of the camera lens determines how dark the stone looks.

These phopto's are what a person with a face the same colour as a camera lens (dark skinned, black hair) would see at about 14 inches.

Many other instruments work on a very close up approach and this results in reduced bright areas, which i think is wrong. Very few people look at diamonds from 6 - 9 inches away in everyday life.

 

[caratgirl]

Actually, I am pretty interested in the answer to the HCA of .3 or so as well. I've never seen one like that so I am curious. Does it always mean lack of contrast and not much fire?

 

[Mara]

Brian at WhiteFlash has said the same thing about less contrast with HCA scores under 0.6. He isn't often on the board...but maybe he will find this thread and chime in.

 

[Garry H (Cut Nut)]

Brian and I beg to differ on this one. But we enjoy sharing a bottle of wine.

I guess it depends on whether you think size counts, and how big your head is?

Now Mara I can do no more than that to get Brian to drop in

 

[fire&ice]

I don't have any of the information in front of me as it's in the safety dep. box. My little ball of fire scored a .5 on hca last year. I get tons of compliments from people in the trade. The last appraiser wanted to buy it from me when I received the family ring. He said (early 90's) that it was one of the best cut stones he has seen & that was fairly rare. I think it's beautiful; but, the trade has confirmed it over & over again.

 

[Mara]

It just might work Garry

To be really honest..I would LOVE to see Garry and Brian discuss this in forum. I think this question has been asked before...and we don't have a clear picture of the differing sides of the coin. I know Brian is verry busy, but maybe the scent of virtual wine will stir him to enter.

 

[derekinla]

Come on Garry, at least tell us your side of the story. I want to know why an HCA 0.3 gets a 0.3. ... Here's a bottle of *Virtual Cabernet Sauvignon*

 

[Mara]

Garry works best when inbibing Trappist beers.

 

[derekinla]

How about a perfectly poured pint of Guinness????

 

[Garry H (Cut Nut)]

A shallow guiness

 

[Garry H (Cut Nut)]

very shallow guinness

(Actually I can not drink that stuff Derek - you will need to do better, not mad on Cab Sav either)

I had a hard day and need a drink

 

[Garry H (Cut Nut)]

Does this help?

 

[Mara]

Sweet! My diamond is right on the sweet spot.

29.9 crown angle


41.1 pav angle

 

[cherry]

What about my stone? It's 34.8/40.9 just outside the sweet spot. But the idealscope image just look perfect, barely see any light leakage at all.

 

[aljdewey]

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On 1/24/2004 7:32:58 AM cherry wrote:





What about my stone? It's 34.8/40.9 just outside the sweet spot. But the idealscope image just look perfect, barely see any light leakage at all.
----------------

Look at the chart again....yours appears to fall somewhere on the line, which I wouldn't consider "outside".

 

[Mara]

The sweet spot is not JUST on the line....check out the arrows images...you can see which would be considered excellent using those, and the lines as guides. 34.8 and 40.9 should be an amazing stone when coupled with that idealscope image. No worries at all.

 

[Rhino]

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On 1/24/2004 7:32:58 AM cherry wrote:





What about my stone? It's 34.8/40.9 just outside the sweet spot. But the idealscope image just look perfect, barely see any light leakage at all.
----------------

I am curious as to how to interpret the gemological information from this picture. Did the person who took the pic tutor you in how to interpret the data from this image? I am not saying it's bad nor am I saying it's good either. The thing is how does one know? The white or pale reds under the table, no black arrow heads, white on some arrow shafts, what does this mean regarding this stone? I'd be curious to hear the interpretation as this image is not typical of most is images I've seen. Curious.

 

[cherry]

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On 1/24/2004 3:33:37 PM Rhino wrote:

----------------
On 1/24/2004 7:32:58 AM cherry wrote:



What about my stone? It's 34.8/40.9 just outside the sweet spot. But the idealscope image just look perfect, barely see any light leakage at all.
----------------

I am curious as to how to interpret the gemological information from this picture. Did the person who took the pic tutor you in how to interpret the data from this image? I am not saying it's bad nor am I saying it's good either. The thing is how does one know? The white or pale reds under the table, no black arrow heads, white on some arrow shafts, what does this mean regarding this stone? I'd be curious to hear the interpretation as this image is not typical of most is images I've seen. Curious.----------------

What do you mean the idealscope image is not typical of most images?

I got this image from Brian, whiteflash regarding to the stone which I am going to purchase. Brian said that idealscope image looks prefect and no light leakage.
But do you mean that it's not the real idealscope image?

 

[mdx]

Hi Gary

In terms of your graph I think the lines representing the Max and Min crown angles plotted on the pavilion angle axis are too straight. As for the sweet spot being center and also straight, well I don’t know.

What I think is needed is a dramatic increase in the volumetric amount of “Penfold” on the table so we can get some curves in the graph.
It is after all weekend

Hehe sorry lads it's an “Aussie” thing

Johan

 

[fire&ice]

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On 1/24/2004 7:17:57 PM mdx wrote:

Hi Gary


What I think is needed is a dramatic increase in the volumetric amount of “Penfold” on the table so we can get some curves in the graph.
It is after all weekend

Hehe sorry lads it's an “Aussie” thing

Johan
----------------

This Shiela can interpretate!

 

[hoorray]

So can this one, and I'm having some Penfolds as I type to help that process.

 

[Garry H (Cut Nut)]

Yes that chart was done very hastily Johan - please no one buy diamonds based on it!!!

And for all those in our bottle necking part of the woods - a little birdy told me that Annies Lane and a Coonawarra and somthing else will be on sale at Safeway / Woolies for A$12 soon

Yumm yumm

 

[hoorray]

Yummmmm...hubby wants to know if RWT will go on sale soon

.

 

[Stephan]

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On 1/24/2004 7:32:58 AM cherry wrote:

What about my stone? It's 34.8/40.9 just outside the sweet spot. But the idealscope image just look perfect, barely see any light leakage at all.----------------

Yes, but does someone have pictures of shallow diamonds with a very low score on the HCA?

 

[Garry H (Cut Nut)]

What is RWT ?

 

[Mara]

Garry I think what Stephan meant by 'very low' is a score of 0.3...the stone you posted looks like it has a score of 4.5 HCA?




Any examples of a *very* shallow type stone that would be high on light return but less on contrast with a low HCA score? Mine is like that....but it's a 2.8 on HCA so doesn't qualify!

Also Derek's original post was requesting an image of a stone that had AGS0 numbers, but had a shallower cut to it, with a very low HCA score of .5 of under. Any DiamCalc's of something like that?

 

[Garry H (Cut Nut)]

Sorry, thanks for pointing that out Mara.
Try this one.
The DiamCalc score is still a work in progress. Sergey has a complex mathematical formula that uses all the #’s multiplied by square roots etc and this stone scores very well. But of course it gets a lower HCA score than a Tolkowsky stone because It has a better spread.

 

[derekinla]

Garry,

What a strange coincidence. The DiamCalc example you posted has the EXACT specs for the stone I purchased for my fiance.

1.404 G SI1 AGS 000 HCA = 0.3
7.27 x 7.31 x 4.38mm
Table 56%
Crown 33.9 degrees
Pavillion 40.5 dgrees
Girdle 0.7% to 1.4%

 

[derekinla]

One more pic.