HCA 2.5- No good?

[sugarplum]

Hi All,

This stone scored a 2.5 on the HCA. Should I pass on it?

Table: 55%
Depth: 61.8%
Crown angle: 35.5
Paviliion angle: 40.8
Girdle: Thin-Medium
Stars: 50%
LGF: 80%

And how terrible is a 2.5? Would it still perform well (just not as nicely compared to stones that score under a 2)?

 

[strmrdr]

I probably would pass.
That''s not a combo I like.

 

[sugarplum]

Hi Strmrdr- What do you think could''ve improved this combo? The crown angle?

 

[enbcfsobe]

The crown angle is a little high. I think 34.5 is where the excellent range tops out for CAs. That said, I have the same crown/pav angles but my table is 57. This gets it to a 2.5 or 2.6 as well on the HCA, but I went with it anyway. I'm not sure what exactly the effect is of a slightly larger table -- maybe better spread?
In any event, while you could probably do better in terms of specs, don't lose sight of the fact that you should be picking what you like best. I only felt comfortable with my decision after comparing mine to some that had HCA scores by the numbers. I still liked the look of mine better or at least equally in various lighting situations. It is worthwhile to do these kinds of comparisons (and definitely to get it out from under the store lights!) before making a call. Despite being only VG on the HCA, that VG gets me loads of compliments about how sparkly my stone is (and it is sometimes almost embarassing to compare to some of the super-deep, lifeless stones some of my friends and colleagues have -- too bad they didn't have any PS help!)

 

[sugarplum]

Date: 6/15/2007 12:48:59 PM
Author: sugarplum
Hi Strmrdr- What do you think could''ve improved this combo? The crown angle?

Also, you personally don''t like the combo but the stone isn''t terrible is it?

The HCA comment of "worth buying if price is right" kind of makes it seem like a bad stone...

but 2.5 isn''t thaaat high up. I''ve seen a stone in person before that looked nice so I was surprised when I punched the numbers in to find that it scored a 4.5 on the HCA.

 

[sugarplum]

Date: 6/15/2007 1:08:19 PM
Author: enbcfsobe
The crown angle is a little high. I think 34.5 is where the excellent range tops out for CAs. That said, I have the same crown/pav angles but my table is 57. This gets it to a 2.5 or 2.6 as well on the HCA, but I went with it anyway. I''m not sure what exactly the effect is of a slightly larger table -- maybe better spread?
In any event, while you could probably do better in terms of specs, don''t lose sight of the fact that you should be picking what you like best. I only felt comfortable with my decision after comparing mine to some that had HCA scores by the numbers. I still liked the look of mine better or at least equally in various lighting situations. It is worthwhile to do these kinds of comparisons (and definitely to get it out from under the store lights!) before making a call. Despite being only VG on the HCA, that VG gets me loads of compliments about how sparkly my stone is (and it is sometimes almost embarassing to compare to some of the super-deep, lifeless stones some of my friends and colleagues have -- too bad they didn''t have any PS help!)

Hi enbcfsobe- Glad to hear that your stone worked out. My BF and I have decided to purchase online so the numbers mean a lot since we can''t see the actual stone before we buy it. We don''t want to buy something and end up having to ship it back and go through that process.

I know it''s difficult to find a stone that matches every aspect of one''s criteria. This particular one came closest to our criteria so I was bummed when it scored a 2.5 on the HCA. That''s why I''m wondering if this combo of numbers and a 2.5 on the HCA makes this a stone I should stay away from. My BF thinks I''m splitting hairs.

 

[JohnQuixote]

Date: 6/15/2007 12:06:22 PM
Author:sugarplum


Hi All,

This stone scored a 2.5 on the HCA. Should I pass on it?

Table: 55%
Depth: 61.8%
Crown angle: 35.5
Paviliion angle: 40.8
Girdle: Thin-Medium
Stars: 50%
LGF: 80%

And how terrible is a 2.5? Would it still perform well (just not as nicely compared to stones that score under a 2)?

Not terrible. Garry is revising the HCA and some of the current 2.X numbers will become included the recommended range.

The CA/PA combination is not what we're accustomed to seeing around here but it isn't bad. These proportions would receive GIA EX and the AGS cut guidelines predict AGS1 (the actual grades would depend on particulars). By the numbers it would be be a good performer, probably quite fiery. Do you have an ideal-scope image?

 

[kcoursolle]

It''s taking a hit because of the higher crown angle. If you really like this stone, then we need to see ideal scope images.

 

[strmrdr]

Date: 6/15/2007 1:16:18 PM
Author: sugarplum

Date: 6/15/2007 12:48:59 PM
Author: sugarplum
Hi Strmrdr- What do you think could''ve improved this combo? The crown angle?

Also, you personally don''t like the combo but the stone isn''t terrible is it?

The HCA comment of ''worth buying if price is right'' kind of makes it seem like a bad stone...

but 2.5 isn''t thaaat high up. I''ve seen a stone in person before that looked nice so I was surprised when I punched the numbers in to find that it scored a 4.5 on the HCA.

In general I agree with the hca with a discount over the best of the ideal cuts its worth a look but compare it too an ideal cut.
I don''t care for the look of these high crown angle, midrange to deepish ideal range pavilion stones.
High crown angles work better with shallower pavilions.
Where the hca errors is with pavilion angles in the 41.x range with 34 to 34.5 crowns.

 

[enbcfsobe]

while i''m really happy w/ my stone, if i was buying online and had endless options with tons of great info like idealscopes and asets and close-up pics, i would probably try for something within the 1-2 range on the HCA. i bought locally, so the availability of lots of things to look at and things to compare was different, but the overall number of stones in the ideal to super-ideal range was relatively small.

 

[sugarplum]

I don''t have an idealscope image of this stone.

 

[sugarplum]

Date: 6/15/2007 1:46:51 PM
Author: JohnQuixote

Date: 6/15/2007 12:06:22 PM
Author:sugarplum



Hi All,

This stone scored a 2.5 on the HCA. Should I pass on it?

Table: 55%
Depth: 61.8%
Crown angle: 35.5
Paviliion angle: 40.8
Girdle: Thin-Medium
Stars: 50%
LGF: 80%

And how terrible is a 2.5? Would it still perform well (just not as nicely compared to stones that score under a 2)?

Not terrible. Garry is revising the HCA and some of the current 2.X numbers will become included the recommended range.

The CA/PA combination is not what we''re accustomed to seeing around here but it isn''t bad. These proportions would receive GIA EX and the AGS cut guidelines predict AGS1 (the actual grades would depend on particulars). By the numbers it would be be a good performer, probably quite fiery. Do you have an ideal-scope image?

Hi John- Will this CA/PA combination affect the stone''s color?? It''s an F, 1.55 cts. If I''m paying for an F, I want it to face up like an F should--white! I''ve seen an F color stone with a 34 degree CA and 41.6 PA...it was not a pretty sight. It was yellow because of the deep PA! I think it traumatized me...

Now I make sure I stay away from any CA/PA combos that might turn a colorless stone yellow!

 

[diamondseeker2006]

The cut does not affect the color negatively. A great cut can make a stone appear brighter in certain light, but the color is not going to be worse because it is not ideal cut. I have an old stone that is far from ideal cut and it is an F color, and it is as white as can be! Low colors may benefit from a great cut, but colorless stones are colorless no matter the cut!!!

 

[JohnQuixote]

Date: 6/16/2007 4:16:11 AM
Author: sugarplum

Hi John- Will this CA/PA combination affect the stone's color?? It's an F, 1.55 cts. If I'm paying for an F, I want it to face up like an F should--white! I've seen an F color stone with a 34 degree CA and 41.6 PA...it was not a pretty sight. It was yellow because of the deep PA! I think it traumatized me...

Now I make sure I stay away from any CA/PA combos that might turn a colorless stone yellow!

No. As DS said, a colorless diamond won’t show color. The "F" you're reporting should not have been an F by GIA/AGS standards if you perceived yellow. At 41.6/34 a stone could appear dark if you held it very close (due to head shadow) but that's not a combination that entraps body color. What you saw may also have been influenced by the shirt were you were wearing, what was in the background, what colors were on the wall and ceiling, the signage around you, etc.

A poorly cut DEF can look lifeless or dark, but 40.8/35.5 would not cause that. It would help to have an ideal-scope image of course.

Just for the record, there are configurations which cause color to be trapped more when present. More about that here.

 

[sugarplum]

Date: 6/16/2007 10:59:21 AM
Author: JohnQuixote

Date: 6/16/2007 4:16:11 AM
Author: sugarplum

Hi John- Will this CA/PA combination affect the stone''s color?? It''s an F, 1.55 cts. If I''m paying for an F, I want it to face up like an F should--white! I''ve seen an F color stone with a 34 degree CA and 41.6 PA...it was not a pretty sight. It was yellow because of the deep PA! I think it traumatized me...

Now I make sure I stay away from any CA/PA combos that might turn a colorless stone yellow!

No. As DS said, a colorless diamond won’t show color. The ''F'' you''re reporting should not have been an F by GIA/AGS standards if you perceived yellow. At 41.6/34 a stone could appear dark if you held it very close (due to head shadow) but that''s not a combination that entraps body color. What you saw may also have been influenced by the shirt were you were wearing, what was in the background, what colors were on the wall and ceiling, the signage around you, etc.

A poorly cut DEF can look lifeless or dark, but 40.8/35.5 would not cause that. It would help to have an ideal-scope image of course.

Just for the record, there are configurations which cause color to be trapped more when present. More about that here.

John, that 41.6/34 F stone was white under a diamondlite but when you took it out--yellow! We put it up next to a G and the G was so so so much whiter than the F.

I don''t have an ideal scope image of the 40.8/35.5 I''m considering...wish I did. How exactly does a higher crown angle (i.e. 35.5) affect a stone?

 

[strmrdr]

Where some confusion comes in is the color grade is the color of the material and except in fancy colored diamonds not the face up color.
Its graded face down.
Cut can effect the face up tone of the diamond with badly cut diamonds appearing darker.
But its still the same color.

 

[JohnQuixote]

Date: 6/16/2007 1:43:33 PM
Author: sugarplum

John, that 41.6/34 F stone was white under a diamondlite but when you took it out--yellow! We put it up next to a G and the G was so so so much whiter than the F.

I don't have an ideal scope image of the 40.8/35.5 I'm considering...wish I did. How exactly does a higher crown angle (i.e. 35.5) affect a stone?

Sorry Sugarplum, my mistake. As I was typing 41.6/34 this morning I was thinking 40.6/34, thus my comment about head shadow. Give me a redo... That combo could indeed look dark. It shouldn't look yellow (not a GIA/AGS F) but a well-cut G would certainly look brighter. As was said above, cut can affect the face-up tone.

The 55% table and 35.5 crown angle combine to make it fiery; lots of colored flashes. If you can, compare it to a larger tabled shallow-crowned stone (near 60% table, 60% depth - very common and bright) and a modern Tolkowsky (56-57, 40.8, 34.5). You'll have three cool diamonds to look at. They should be similar color/clarities. View them in several lighting conditions as you're able. If all perform well you should see character differences between the 40.8/35.5 and the 60/60 pretty easily. The 40.8/35.5 and Tolk will be much closer; the primary technical diff is that Tolks have crown height near 15% and yours is closer to 16%. A pinch more fire maybe - just be sure it's bright enough for you compared to the Tolk.

 

[kcoursolle]

Date: 6/16/2007 1:05:59 AM
Author: sugarplum
I don''t have an idealscope image of this stone.

You have to ask the vendor for one.

 

[Ellen]

Date: 6/15/2007 1:46:51 PM
Author: JohnQuixote

Not terrible. Garry is revising the HCA and some of the current 2.X numbers will become included the recommended range.

The CA/PA combination is not what we''re accustomed to seeing around here but it isn''t bad. These proportions would receive GIA EX and the AGS cut guidelines predict AGS1 (the actual grades would depend on particulars). By the numbers it would be be a good performer, probably quite fiery. Do you have an ideal-scope image?

John, I am not so sure of that now...

https://www.pricescope.com/community/threads/revisions-to-the-hca.61038/

 

[sugarplum]

Date: 6/16/2007 5:29:06 PM
Author: JohnQuixote

Date: 6/16/2007 1:43:33 PM
Author: sugarplum

John, that 41.6/34 F stone was white under a diamondlite but when you took it out--yellow! We put it up next to a G and the G was so so so much whiter than the F.

I don''t have an ideal scope image of the 40.8/35.5 I''m considering...wish I did. How exactly does a higher crown angle (i.e. 35.5) affect a stone?

Sorry Sugarplum, my mistake. As I was typing 41.6/34 this morning I was thinking 40.6/34, thus my comment about head shadow. Give me a redo... That combo could indeed look dark. It shouldn''t look yellow (not a GIA/AGS F) but a well-cut G would certainly look brighter. As was said above, cut can affect the face-up tone.

The 55% table and 35.5 crown angle combine to make it fiery; lots of colored flashes. If you can, compare it to a larger tabled shallow-crowned stone (near 60% table, 60% depth - very common and bright) and a modern Tolkowsky (56-57, 40.8, 34.5). You''ll have three cool diamonds to look at. They should be similar color/clarities. View them in several lighting conditions as you''re able. If all perform well you should see character differences between the 40.8/35.5 and the 60/60 pretty easily. The 40.8/35.5 and Tolk will be much closer; the primary technical diff is that Tolks have crown height near 15% and yours is closer to 16%. A pinch more fire maybe - just be sure it''s bright enough for you compared to the Tolk.

John- Would a 40.8/35.5 look much darker than a Tolk? Or would the difference only be slight? I know a deep PA can make a stone look darker so does a higher CA have any specific effects on a stone? Thanks!

 

[Garry H (Cut Nut)]

John Q is correct, the ideal-scope image of this stone and symmetry could save it.
It probably has a nice amount of fire - but if there are symmetry issues i would pass on it

 

[Regular Guy]

Date: 6/24/2007 2:26:52 AM
Author: Garry H (Cut Nut)
John Q is correct, the ideal-scope image of this stone and symmetry could save it.
It probably has a nice amount of fire - but if there are symmetry issues i would pass on it

Garry, would the IS looking good only be consistent with the non-leaky scores accepted by the current HCA cut-off?

Would a binocular IS be needed to get the more expanded range you might prefer to include?

if the latter is true, any advice for making more practical consideration for options above 2?

Thanks,