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33 crown and 40.8 pavilion?

What is the HCA score on it?
 
“Denied access” ??
 
Add me to the denied list, lol.

Either way -- why a 33/40.8 combo? What is the reasoning? IMO, the crown is too shallow and pavilion not steep enough to offset the crown so it's not the most complimentary angle, but it's not horrible either.

Which gets me back to, why this stone?
 
It’s a 2.6ct H/VS1
T55/D60.8/CA33/PA40.8
HCA0.7
GIA #1315761687
$28.5k

Video looks dreamy. ;)2
 
OoohShiny said:
What is the HCA score on it?
Click to expand...
sledge said:
Add me to the denied list, lol.

Either way -- why a 33/40.8 combo? What is the reasoning? IMO, the crown is too shallow and pavilion not steep enough to offset the crown so it's not the most complimentary angle, but it's not horrible either.

Which gets me back to, why this stone?
Click to expand...
I don’t know I need help I’ve been looking for a perfect stone for a very long time but I can’t get anywhere I have $30K budget hoping to get the stone as close to 3 carats with GIA
 
Numbers look good to me!
 
bmfang said:
It’s a 2.6ct H/VS1
T55/D60.8/CA33/PA40.8
HCA0.7
GIA #1315761687
$28.5k

Video looks dreamy. ;)2
Click to expand...
Interesting - don't often seem to get small tables with low crown angles??

Should look bigger for its carat weight if it's a shallow stone!
 
@Monkey1229 , hi, I’m not sure if this is allowed, @psadmin please delete if not, I’m kind of a newbie so sorry if I’m violating any rules. I have a GIA triple x 2.82ct (9.05 x 9.09) J SI1 eye clean (table 58, ca 34, pa 40.8) that I’m trying to sell so I could get myself a crafted by infinity. Would you be interested? I havent listed it anywhere yet, only started thinking’s about it last week.:razz:
 
PA 40. 8 why did it show up as an emoji?
 
sledge said:
Add me to the denied list, lol.

Either way -- why a 33/40.8 combo? What is the reasoning? IMO, the crown is too shallow and pavilion not steep enough to offset the crown so it's not the most complimentary angle, but it's not horrible either.

Which gets me back to, why this stone?
Click to expand...

Just to note 40.8 is nicely complementary to 33. 40.8 is compatible with a wide range of shallower crowns than yours expect.

Garry H said:
say 40.75 P and 34.5 C is ideal , then for every 1 degree + pavilion angle subtract 5 degrees from the crown angle.
Click to expand...

So you can see the pavilion is highly compatible with various angles.

34.5 / 40.75 transformed using the above fornula 33.25/40.8
 
gm89uk said:
Just to note 40.8 is nicely complementary to 33. 40.8 is compatible with a wide range of shallower crowns than yours expect.



So you can see the pavilion is highly compatible with various angles.

34.5 / 40.75 transformed using the above fornula 33.25/40.8
Click to expand...

I’m not following that formula that Garry mentioned. Is it every +/- 1 degree of crown angle, you -/+ 0.05 degrees pavilion angle?
 
bmfang said:
I’m not following that formula that Garry mentioned. Is it every +/- 1 degree of crown angle, you -/+ 0.05 degrees pavilion angle?
Click to expand...

I got lost on Gary’s formula too and am sure it’s missing a decimal or two ???
 
kmoro said:
I got lost on Gary’s formula too and am sure it’s missing a decimal or two ???
Click to expand...

The decimal point is not important. It's just saying an inverse correlation between pavilion and crown at a ratio of 1:-5.

IE for every 0.1 pavilion you increase, the crown should roughly twicer by 0.5 starting at a rough base of 34.5 /40.75. Obviously this isn't exact as 35/40.8 work well.
 
cowcow81 said:
@Monkey1229 , hi, I’m not sure if this is allowed, @psadmin please delete if not, I’m kind of a newbie so sorry if I’m violating any rules. I have a GIA triple x 2.82ct (9.05 x 9.09) J SI1 eye clean (table 58, ca 34, pa 40.8) that I’m trying to sell so I could get myself a crafted by infinity. Would you be interested? I havent listed it anywhere yet, only started thinking’s about it last week.:razz:
Click to expand...

You will need to create a LoupeTroop (spelling?) or Diamond Bistro listing then link to it from the Pre-Loved section of this forum - you are not allowed to post personal contact details on here so it has to be on the LT and DB listing.
 
cowcow81 said:
PA 40. 8 why did it show up as an emoji?
Click to expand...

Because you used the parenthesis symbols to capture the data. The ) symbol combined with an 8 and no space between them results in such action.

With space: 8 )
No space: 8)

gm89uk said:
Just to note 40.8 is nicely complementary to 33. 40.8 is compatible with a wide range of shallower crowns than yours expect.

So you can see the pavilion is highly compatible with various angles.

34.5 / 40.75 transformed using the above fornula 33.25/40.8
Click to expand...

I hadn't seen that ratio that Garry posted. I wasnt saying it doesn't have an inverse relationship. I just think it needs a little more steepness to either the crown or pavilion to balance properly. 34/40.8, 33/41, 33.5/40.9, etc

I didn't run the math as I'm mobile but I'm guessing those fall within the ratio suggested by Garry.

Also even by his own ratio math, a 33.25/40.8 works as you pointed out. A GIA reported value of 33 where we know rounding and averaging occurs seems likely to have a a few actual crown readings less than 33, which would then depend how the offsetting pavilion actuals read. 32.8/40.7 would be worse but 32.8/40.9 may counter the effect.

I just see it as a borderline stone is all. This is one I'd personally want a SARIN report so I could see all the actual values. Or at least confirmation via other advanced imaging.

The above point I am trying to note seems in line with the AGS proportions chart. The exact proportions lands in excellent, but going out a reasonable degree of accuracy we can see there is about a 33% chance it goes ideal. But if cutting gets sloppy its knocking on VG territory.

Screenshot_20190503-072931_Sheets.jpg
 
@sledge, You'll notice HCA is much more tolerant of shallow combinations than AGS. If you plugin 33/40.5 you'll still hit excellent.
 
gm89uk said:
@sledge, You'll notice HCA is much more tolerant of shallow combinations than AGS. If you plugin 33/40.5 you'll still hit excellent.
Click to expand...
19 years ago when I developed HCA I was first to factor spread into a grade.
Bigger diamonds are more desirable than smaller ones.
So along with beauty factors, I include spread which lowers HCA scores (e.g. Tolkowsky gets around 0.4 spread penalty.
All other labs use spread or depth 5 as a grade lowering factor when it is too small.
I believe I am right and they are wrong.
Now with Looks Like added to HCA - the spread computation is dead accurate - not based on rounded data and trigonometry.
 
33 works with 40.8 and with 60 table is one of the better 60/60 combos ags0 potential.
When talking a modern ideal cut its a bit shallow, anything under 34 is a bit shallow.

Garry I think your formula is being misunderstood.
It says that the inverse crown relationship is the same between the 2 using your formula.
That does not mean they are equivalent because the CH is different and the uppers are also impacted as well as lgf angle..
Remember there are 5 things that set the upper girdle angles: table size, crown angle, star length, and painting/digging.
As you move the crown angle up and down they have to be taken into account.

Likewise moving the pavilion angle moves the lower girdle angles for any given lgf%.
You can run into lower girdle angle issues even is the pavilion mains angle and crown angle inverse relationship is good.
While the crown pavilion angle relationship is the building block it is not the whole story.

It also works for a narrow range of angles then it fails to produce a good looking diamond the larger the table the sooner it fails.

So the bottom line dont use the formula as this one is good so another one that follows the formula is also good.
It is more of an academic study or part of a bigger whole than useful for selection.
 
Karl_K said:
33 works with 40.8 and with 60 table is one of the better 60/60 combos ags0 potential.
When talking a modern ideal cut its a bit shallow, anything under 34 is a bit shallow.

Garry I think your formula is being misunderstood.
It says that the inverse crown relationship is the same between the 2 using your formula.
That does not mean they are equivalent because the CH is different and the uppers are also impacted as well as lgf angle..
Remember there are 5 things that set the upper girdle angles: table size, crown angle, star length, and painting/digging.
As you move the crown angle up and down they have to be taken into account.

Likewise moving the pavilion angle moves the lower girdle angles for any given lgf%.
You can run into lower girdle angle issues even is the pavilion mains angle and crown angle inverse relationship is good.
While the crown pavilion angle relationship is the building block it is not the whole story.

It also works for a narrow range of angles then it fails to produce a good looking diamond the larger the table the sooner it fails.

So the bottom line dont use the formula as this one is good so another one that follows the formula is also good.
It is more of an academic study or part of a bigger whole than useful for selection.
Click to expand...
Could you have another go at this Karl? Very hard to understand!
 
Garry H (Cut Nut) said:
Could you have another go at this Karl? Very hard to understand!
Click to expand...
I think Karl is saying that one cannot rely on the fixed relationship between crown and pavilion angles - where one falls, the other rises - alone, because the table size, LGF length and other factors need to be taken into account??
 
OoohShiny said:
I think Karl is saying that one cannot rely on the fixed relationship between crown and pavilion angles - where one falls, the other rises - alone, because the table size, LGF length and other factors need to be taken into account??
Click to expand...
Basically yes.
It is limited by other factors than just crown/pavilion inverse angle relationships.
The larger the table the smaller the range of angles that will work well.
 
OoohShiny said:
I think Karl is saying that one cannot rely on the fixed relationship between crown and pavilion angles - where one falls, the other rises - alone, because the table size, LGF length and other factors need to be taken into account??
Click to expand...
Well yes, and that holds for any set of proportions. But the major factor is the inverse crown and pavilion angle relationship. I discovered it in the 1980's and tried hard to get the GIA 'Brilliance' 1998 article researchers to understand it. But geochemists are not great physicists.
I sent them this chart with my drawn in black lines.
It was not really until Al Gilbertson joined them a few years later that I think they Got It.
Fig 11 WLR2.jpg
 
@Garry H (Cut Nut) So why is no one making 27.5/41/53t?

The ''redder" represents HCA? I miss your higher resolution graphs
 
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