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Spread?

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Meraj

Rough_Rock
Joined
Jun 7, 2003
Messages
73
Can someone explain "spread" and how it affects how big the diamond looks. How would I know? Someone said to make sure not get a thick girdle because its not getting my $ worth as then most of the cut weight would be there. So what else and where and what numbers will tell me if the "spread" is acceptable or not. I''m getting confused.
 

Rank Amateur

Brilliant_Rock
Joined
Feb 26, 2003
Messages
1,553
"Spread" is the apparent diameter for a given weight.

Imagine a 1.00 ct stone with a really thick girdle and a high depth %. It's diameter might be 6.20 mm. A really well cut 1.00 ct with a thin girdle might have a diameter of 6.5mm. The better cut stone with the larger diameter is said to have a bigger spread. Some people might think a stone with a larger table "looks more spready" than a smaller table stone with the same girdle diameter. You want a stone with a good spread so that in the face up position it appears as large as possible.
 

niceice

Brilliant_Rock
Joined
Jan 29, 2003
Messages
1,792
Spread can also mean that the diamond was cut so that it has a shallow depth and a wider diameter than a diamond of the same carat weight which has been cut to a better balance of diameter and depth would have... The "ideal" diameter for an ideal cut one carat diamond is about 6.5 mm but you could cut the same piece of rough with a shallower depth and end up with a one carat diamond that had an outside diameter of 6.8 mm and that would be "spread" and it would likely lack a lot of the brilliance, dispersion and scintillation that it would have had if it had been cut properly...
 

Mara

Super_Ideal_Rock
Joined
Oct 30, 2002
Messages
31,003
My stone has a spread...it's a shallow depth and large tabled stone combined with a thin-medium girdle. It's crown angle is very shallow, under 30 degrees. What this means is that the stone was cut not to 'ideal' proportions but rather it was cut to maximize the visual size of the stone. It's a 1.25c which should have a diameter of around 7mm if it was cut in an 'ideal' fashion. But it has a diameter of average 7.16mm which looks more like a 1.35c stone. So for all intents and purposes, my stone LOOKS like a 1.35c stone to the naked eye. But its carat weight only weighs 1.25c. Tricky but fun.

Some are advocates for a cut like this, some most likely think it's a waste of a good stone! It's definitely a preference, as my stone is not like the typical Hearts and Arrows with perfect symmetry. It has 'character' as we like to call it...but it's definitely a preference.

If you are looking for a well cut stone, you should stay away from a thick girdle, a too deep pavilion (e.g. 65% is very deep!), possibly a too large table (e.g. 64% is very large), and know what proportions you should be looking at to begin your search. The tutorial on Pscope will be very helpful!

Also Rich Sherwood posted a chart recently that had diameters of what carat stones should have if they are well cut. That may help guide you in your search. E.g. 1c stone should have diameter of 6.5mm. If it has 6.30...that means its probably carrying extra weight in its pavilion and you are not seeing any of that weight in the top part of the stone. On the same token, opposite...if a 1c stone has a mm of 6.60..it's probably got a larger table and shallower depth.

Good luck!
 

Meraj

Rough_Rock
Joined
Jun 7, 2003
Messages
73
Mara,do you have the site address where Sherwood had this chart you are speaking of? Also, on a GIA or other reports they state "one number X another number" so which one shows the spread? Sorry I'm a novice.

I'm with you when it comes to getting a bigger looking stone out of a smaller carat but does this mean there is more light leakage because its not ideally cut? Thanks!
 

Lanee

Brilliant_Rock
Joined
Jan 29, 2003
Messages
534
Bump, I want to know what thread Sherwood posted that on too.
 

jlim

Shiny_Rock
Joined
Apr 29, 2003
Messages
250
Is this what you are looking for Lanee?

https://www.pricescope.com/community/threads/need-help-with-measurements.7050/
 

Mara

Super_Ideal_Rock
Joined
Oct 30, 2002
Messages
31,003
AJ--

Yes the general feeling is that if you cut a stone with a larger spread and shallower depth, the stone is not as well cut as it could be. I think it really depends on the dimensions of the stone as I have seen some great larger spread stones and some that just are dull or have a fisheye etc. Our stone is pretty well cut, I am very happy with it, but under the IdealScope, it does show more light leakage than an Ideal (OF COURSE) but the IS image is still better than some others I have seen online!! However, we bought the stone in person and while I was originally looking online for a more 'ideal' cut stone, this stone spoke to my fiance and myself...and we really liked the spread of the stone for the same cost. Compared against an 'ideal' 1.0 HCA scoring stone of the same ctw, this stone just looked bigger, was just as sparkly, and my fiance could not tell a difference between the two besides the visual size. So we went with a less ideal stone for these reasons. Sometimes I think....awww I should have just gotten an H&A or similar, but we both really love our stone! It's different.

It's definitely a preference thing. To find a well cut stone with larger spread, I think you have to do alot more research. You can't just look at the dimensions and say...oh that looks bigger than it would if it was well cut, it must be a stone with spread, so I'll get it. Chances are high that it may be a crappily cut large spread stone, no fun at all. IdealScope images and Bscope will help as well.

I think Jonathan at GOG has one of these type stones on his site...I think it was a 1.34 H VS2 or something along those lines, with a good IdealScope and decent Bscope results (I think it was H for all 3) and the price was something like $5500! I don't know if it is sold now, but it was on there for a few months. Amazing....so it's also great for people on a budget who want to get a good stone that may not necessarily be 'ideal' by its specs.

Also dimensions are the 1 - 2 x 3 (or sometimes it will look like 1 x 2 x 3)

1= diameter smallest
2= diameter largest
3=depth

That means that when the stone was measured all the way around, it was found to have the smallest top diameter of (1) and the largest diameter of (2) with a depth of (3). An example would be a stone with 7.12 - 7.15mm diameter and 4.25mm depth. That means that the 'variance' for the diameter of the stone is only .03mm which is excellent for a round. You don't want the stone to be 'out of round' meaning that say...that same stone had 7.12 - 7.25 for the diameter. That means its definitely nowhere close to being round (perfect round would be 7.12 - 7.12 or maybe 7.12 - 7.13) and probably looks a little out of round to your eye!

Hope that is not confusing and helps

 
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