shape
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About to lose my mind........

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NeedHelp

Rough_Rock
Joined
Oct 16, 2002
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15
I think I have read and seen to much.
Now I will ask for help from some of you folks that know what's what.
My budget is from $2700 - $3300
I am finding all sorts of stones from .74 to .90
Can you suggest a stone please!!!
This will give me an idea if I am in the right state of mind.
I am looking for round, G to H, SI1, I guess.
Someone please respond...

example:
Is this good?

Graded by: GIA
Shape and Cut: ROUND BRILLIANT
Weight: 0.91
Clarity: SI1
Color: H
Dimensions: 6.17 x 6.21 x 3.85 mm
Depth Percentage: 62.2 %
Table: 58 %
Crown: %
Pavilion: %
Girdle: M-STK F
Culet: NO
Polish: GOOD
Symmetry: GOOD
Fluorescence: NONE
Notes:

$ 3357.70

I know there is no crown or pavillion...but all the other stats look pretty good right?
 

NeedHelp

Rough_Rock
Joined
Oct 16, 2002
Messages
15
C'mon guys! 11 Views and not one reply?...
 

peterchristopher

Rough_Rock
Joined
Sep 25, 2002
Messages
42
NeedHelp,

You are going to need crown and pavilion angles to plug into the HCA, you just don't have enough information here. Ask for a Sarin report--GIA certs do not provide this information. It is a lot easier with AGS certs. Once you get that info plug it in yourself here: https://www.pricescope.com/cutadviser.asp. Anything that scores under 2 is good.

Pricewise I don't know if this is a good deal. Have you tried looking for a stone through this site? The prices are very fair and sometimes there are discounts. A simple search will help you compare prices and know what to expect for a stone like this.

Pete

PS Don't forget that cut is the most important of the 4Cs!
 

NeedHelp

Rough_Rock
Joined
Oct 16, 2002
Messages
15
Thanks guys. The stone above has a big spread. I would like 6.1 mm spread. Is that possible with my budget?
If any one posts a link of a stone they picked out in my price range I would really appreciate it. This would give me some insite into what I should look for, or might be the right one.
 

scotch

Rough_Rock
Joined
Oct 15, 2002
Messages
94
Mmh, looks like the crown angle could be a little too large, something like 36.5 degrees plus. Or am I wrong, what do the experts think? That would probably result in a HCA of 2.5 or more. Price looks o.k. though. Just my opinion, I could be wrong...:))
 

Garry H (Cut Nut)

Super_Ideal_Rock
Trade
Joined
Aug 15, 2000
Messages
18,422
Scotch you are better than me - All I can suspect is the combination of C and P may be bad.

We can not know any more.

See the 60:60 on the tutorial and you will know what I mean :)
 

scotch

Rough_Rock
Joined
Oct 15, 2002
Messages
94
Garry, I know what you mean. But the two 60/60 stones in your example, while having the same diameter, would have different carat weights. In this case, we know the carat weight, so there should be only one combination of angles that works. I checked this formula I was asking about earlier using a couple of diamonds with known dimensions. While the pavillion angle was mostly quite on the mark, the crown angle usually was off by 0.5 to 1 degree (lower). I don't know why that is. Furthermore, the problem with the girdle thickness persists. I decided to get diamcalc after all. Hope that works better. I tried to post a spreadsheet with the calculations, but it doesn't take excel files.

Best regards,
Scotch
 

Garry H (Cut Nut)

Super_Ideal_Rock
Trade
Joined
Aug 15, 2000
Messages
18,422
Very clever Scotch approach, sounds like you are terminally hooked :)

Actually because the gridle contains so much of the diamond weight, and we do not know if it is mostly slightly thick or mostly medium, we still have insufficient data.

But hats off to you :)
 

scotch

Rough_Rock
Joined
Oct 15, 2002
Messages
94
Wow! Coming from you, that's a huge compliment. Thanks! You are quite right nevertheless. I think if one had a precise girdle measurement, you could figure out the complete dimensions with reasonable accuracy, at least it would be possible to decide if its worth taking a closer look. The next step would probably be an examination using optical tools. As long as one has only a rough GIA range like "thin to medium" there's no point in even trying.

I've checked a couple things using DiamCalc and my own calculations. I'm not completely unhappy with the results, my crown angles are ususally within 0.5% lower than those of the program, the pavillion angels are even closer. Turns out I was using the wrong density for a diamond, should've used 3.522 g/ cm^3 instead of 3.51. Makes a huge difference.

Coming back to the stone Needhelp was asking about, I have entered the specs into DiamCalc, and the crown angle is indeed too steep. Assuming a 1.7% (slightly thick) girdle gives a 36.8 angle, and you'd arrive at a 2.4 HCA. Taking a thinner girdle makes it only worse. Garry, your first HCA estimate seems to right on the mark.

best regards,
Scotch
 

Garry H (Cut Nut)

Super_Ideal_Rock
Trade
Joined
Aug 15, 2000
Messages
18,422
Thanks Scotch.
I am not as smart as you, but have the benefit of some experiance and a good tool in DiamCalc.

Have you explored making movies, cut quality and ray tracing yet. But the easist tool for cut analysis is the virtuaal ideaal-scope.
 

Richard Sherwood

Ideal_Rock
Joined
Sep 25, 2002
Messages
4,924
Boy you ain't kiddin you're not as smart as Scotch, Garry.

He's almost as smart as me.

Hey Scotch, have you heard the one about how many Australians it takes to change a light bulb?

Six. Five to stand around drinking beer and arguing how best to do it, and one (usually an immigrant) to finally barge in and change the damn thing.


Rich
 

Garry H (Cut Nut)

Super_Ideal_Rock
Trade
Joined
Aug 15, 2000
Messages
18,422
You obviously do not know any Aussies Rich.
After you drink enough you want to turn the light off and have a little sleep.
Before you know it, it is daylight and you do not need the light on.
Repeat the process.
Never change the light bulb.
As they say, Stay drunk, you do not get a hangover :)
 

scotch

Rough_Rock
Joined
Oct 15, 2002
Messages
94
How about this one: What's an Australians idea of an eight-course dinner? - Two Hamburgers and a six pack.

Rich, I'm afraid Garry and I are both smarter than you. As I am a native of Germany, the reason is obvious: It's the beer. The only people smarter than us are the Russians (Hi Leonid). Why? - Vodka. Now you shouldn't think alcohol always makes you smarter, e.g. Gin actually makes you very stupid. (Any Brits around?)

I'm glad we got that all worked out now. :bigsmile:

Scotch
 

GiGi

Rough_Rock
Joined
Oct 8, 2002
Messages
87
Hey you all,

I am a 100% proud Chinese, just from a thing or two my ancestor taught me - Chinese are smarter than all of ya, and WOMEN are definitely smarter than MEN !!!!!!!!:naughty:

GiGi
 

scotch

Rough_Rock
Joined
Oct 15, 2002
Messages
94
Dear GiGi,

o.K., I give you the one about the Chinese. I just wonder what they were drinking that made them so smart. They are probably already too clever to tell anybody else. But women??? Aren't those the people you can get to marry you by giving them little colorless minerals? :))

Yours,
Scotch
 

GiGi

Rough_Rock
Joined
Oct 8, 2002
Messages
87
You are going to ge into A LOT of trouble for saying that...... Watch your behind....:sun:
 

scotch

Rough_Rock
Joined
Oct 15, 2002
Messages
94
:devil: Thanks for the warning, I'll remain seated then for a while...:halo:
 

Richard Sherwood

Ideal_Rock
Joined
Sep 25, 2002
Messages
4,924
Hey Garry, I like your light bulb changing ways. Appeals to my philosophy of the "path of least resistance".

Scotch, I'm afraid Gigi's got us beat. Chinese and woman... Whoa.

I feel like a neandarthal. A British one.

Rich
 
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