Question on why round sapphires are cut the way they are.....

[haagen_dazs]

Hi all
i am starting to venture into coloured gems... down the slippery slope! lol

Question
Based on some the 3D analysis of the sapphires from the nature sapphire company,

why are the white round sapphires cut in a way to mimic RB diamond cutting (ie pavilion facets, etc)

while round other colour sapphires are not cut in this way.
round other colour sapphires are cut with a dome shape hemispherical bottom...

 

[Stone Hunter]

HMMM...In my uneducated opinion I think that the ones cut that way are often used as side stones for colored gems. The center stone could be a Sapphire or something else. That way the side stones have a bit of sparkle, similar to diamond sides but without the expense.

HTH

 

[FrekeChild]

The domed/hemispherical shape is due to cutters trying to maintain weight and depth of color in the stone. This is common at Natural Sapphire company. Someone else can explain it better than I can.

And it''s my understanding that the depth of color is not needed to enhance the beauty of the white stones, like it is for colored stones.

 

[haagen_dazs]

Date: 10/22/2009 1:09:56 AM
Author: FrekeChild
The domed/hemispherical shape is due to cutters trying to maintain weight and depth of color in the stone. This is common at Natural Sapphire company. Someone else can explain it better than I can.


And it''s my understanding that the depth of color is not needed to enhance the beauty of the white stones, like it is for colored stones.

is that the NSC cutting style or is this the way all coloured gems are cut - ie to maximise colour ?

 

[FrekeChild]

Date: 10/22/2009 1:38:53 AM
Author: haagen_dazs

Date: 10/22/2009 1:09:56 AM
Author: FrekeChild
The domed/hemispherical shape is due to cutters trying to maintain weight and depth of color in the stone. This is common at Natural Sapphire company. Someone else can explain it better than I can.

And it's my understanding that the depth of color is not needed to enhance the beauty of the white stones, like it is for colored stones.

is that the NSC cutting style or is this the way all coloured gems are cut - ie to maximise colour ?

This is something that's hotly debated from time to time here in Colored Stones. Most recently, here. Cutting styles generally fall into two types- "Precision cutting" where computer imaging and hi-tech tools are often utilized, and "native cutting" where a stone is cut where it was mined--sometimes by a series of people, and sometimes by less than high-tech instruments. Reading that thread I linked to above will help clarify what I'm trying to say!

I happen to be a big fan of precision cuts, mostly from Dan Stair and Barry Bridgestock, but also Peter Toracca and Gene Flanigan. BUT, in my book, and most colored stoners, color comes first. I have several "native" cut gems that have color that spoke to me. If you check out the Colored Stone eye candy thread, people usually post who cut the stone if it was precision cut.

So the easy answer is that there are all types of cuts--some to maximize color, some to maximize weight, some to maximize "sparkle" with optimal angles for light return, etc. Makes it a lot different from diamond shopping, but more fun too! (Like a treasure hunt!)

ETA: NSC's cuts are often "native" looking--to preserve depth of color and carat weight.

But really, I am not the best person to explain this, so take that all of with a grain of salt!

 

[haagen_dazs]

Makes it a lot different from diamond shopping, but more fun too! (Like a treasure hunt!)

thank you for the link
after 2 months in the rocky forum learning about diamonds, i finally grasp most of the technicalities ( at least i think)
after i came here i am lost again!!

coloured stones are even more complicated than diamonds!!

 

[ma re]

White sapphires are colorless, so brilliance is pretty much everything a cutter wants to bring out from them, that''s why cutters mimic diamond cutting when it comes to whites. But with sapphires that aren''t colorless cutters want to maximize richness of color, and that''s why all kinds of cutting variations are used with those.

 

[chrono]

Colourless stones like diamonds and white topaz/sapphire/zircon/garnet/ etc are cut to make it appear as colourless as possible and also to maximize sparkle. Coloured gemstones are cut differently to showcase the depth and intensity of colour. Cutting for colour requires a certain depth and angles that are usually different from colourless stones. Add to the fact that you also want to avoid windowing, minimize tilt windows, extinction, etc, the cutting issue becomes much more complicated.

 

[Lady_Disdain]

Remember how an excellent cut can make a low colour grade diamond look whiter? In coloured stones, that is not good!

By the way, the cut doesn´t "mimic" round brilliant - it is a round brilliant cut. Other cuts include step cuts (where facets are cut on all on the same tier, in a series of steps up the stone), barion cuts (they have "half moon" facets and can improve sparkle on certain materials), emerald cuts (which I think you know from diamonds) and lots more. There are a lot of fancy cuts that cutters create, with interesting shapes and facet patterns.

Have fun!

 

[haagen_dazs]

so basically there is no set rules / set standards in cutting coloured stones?
do coloured stone cutters use some sort of software to help them or do they just eyeball it after each facet is cut?

i noticed that some of the coloured stones are cut almost haphazardly.

for example, there would be very small oblong thin facet in the middle of 2 big facts...
why did they even shave that down?
there are lots of small tiny facets intersperse among large facets...

i just wonder how do the cutters know what to cut, when to cut, where to cut

 

[chrono]

You''ve asked a very complex question where there is no easy answer. The precision cutters use a software which helps them plan how to cut the stone based on expected results. However, it still takes cutting experience and skill to know how to best utilize the software to do so. "Native" cutting also falls into many categories from the really bad to the very good. There is no one solution because each gem material has different reflective index, inclusions to work around, di or trichroism to work with, etc.

 

[chrono]

Date: 10/22/2009 11:51:00 AM
Author: haagen_dazs
so basically there is no set rules / set standards in cutting coloured stones?
do coloured stone cutters use some sort of software to help them or do they just eyeball it after each facet is cut?

i noticed that some of the coloured stones are cut almost haphazardly.
This sounds more like an example of poor native cutting.
for example, there would be very small oblong thin facet in the middle of 2 big facts...
why did they even shave that down?
there are lots of small tiny facets intersperse among large facets...

i just wonder how do the cutters know what to cut, when to cut, where to cut
It is called years of experience, some by trial and error.

 

[Lady_Disdain]

There are plenty of rules, but they depend on the material type (for example the critical angles vary according to the RI of the material), the effects wanted (to lighten a dark stone, to darken a light stone, to maxime brilliancy, etc) and so on. There are many cutting patterns that can be used (Jeff Graham published many books of design) and softwares that will map the results of a cut by simulating light paths according to the material.

 

[chrono]

I’ve also forgotten to add about an open or closed C axis which dictates what cutting style is best avoided or chosen. There are just too many rules to cover and it’ll make your head spin. Suffice it to say, it isn’t as cut and dry compared to diamond cutting.

 

[movie zombie]

Date: 10/22/2009 1:42:16 PM
Author: Chrono
I’ve also forgotten to add about an open or closed C axis which dictates what cutting style is best avoided or chosen. There are just too many rules to cover and it’ll make your head spin. Suffice it to say, it isn’t as cut and dry compared to diamond cutting.

which makes it more difficult but more fun also!

stones are also cut to maximize size......and the least amount of waste.

nothing wrong with a native cut even if its lopsided as long as that color is what i''m looking for.

mz