Questions about cushion-cuts

[Samara83]

I have a few questions regarding cushion cuts. I'm looking at GIA diamonds, and was first wondering what a cushion cut should read on the certificate. So far I have come across "cushion modified brilliant".

What is the difference between antique/chunky/modern cushion cuts and how can I tell which is which by looking at the GIA certs?

Also, do cushions face-up much smaller than RBCs? Are they more like Asschers in that they face up quite small?

 

[stone-cold11]

Read CCL's cushion guide.
https://www.pricescope.com/forum/ro...s-great-cushion-guideline-thread-t147633.html

Face up, depends on how it is cut.

EDT:
GIA cushion naming convention, also by CCL.
https://www.pricescope.com/journal/new_gia_and_agsl_naming_conventions_cushion_cut_diamonds

 

[Rockdiamond]

HI Samara,
The difference between a cushion brilliant, and a cushion modified brilliant has to do with some larger facets on the back f the diamond in the modified version- where the Cushion brilliant is more like a traditional round brilliant rear facet design.

There are cushions that may face up larger than a round.
You can't use this as a hard ,fast rule, but lower depth stones- say below 65% may be comparable or larger than a round of a similar weight.

BTW- there are also Asscher cuts that face up larger for their weight.......

 

[ChunkyCushionLover]

HI Samara,
The difference between a cushion brilliant, and a cushion modified brilliant has to do with some larger facets on the back f the diamond in the modified version- where the Cushion brilliant is more like a traditional round brilliant rear facet design.

Way off RD reread my article.
https://www.pricescope.com/communit...-conventions-for-cushion-cut-diamonds.147789/

Facets can be added or removed on crown or pavilion altering the brilliant style, they can be large or small earning the description modified.

here are cushions that may face up larger than a round. You can't use this as a hard ,fast rule, but lower depth stones- say below 65% may be comparable or larger than a round of a similar weight.

There is no direct depth comparison than can be made between a cushion and round. Girdle outline, shape of corners, thickness of girdle, type of pavilion structure all have an influence on faceup size.
Depth % in a fancy and a round are calculated differently as well. 65% number is meaningless

 

[Rockdiamond]

I did simplify the differences between Cushion Brilliant, and Cushion Modified Brilliant, that is true. In the majority of cases, the difference has to do with facets added directly below the girdle, on the pavilion.

The depth of a fancy shape is calculated in the exact same manner as a round.....depth divided by width.

As I also mentioned, depth percentage , in and of itself, is not a hard fast rule in determining how "spready" a diamond is- yet more times than not, lower depth does equal greater spread.

 

[ChunkyCushionLover]

I did simplify the differences between Cushion Brilliant, and Cushion Modified Brilliant, that is true. In the majority of cases, the difference has to do with facets added directly below the girdle, on the pavilion.

The depth of a fancy shape is calculated in the exact same manner as a round.....depth divided by width.

As I also mentioned, depth percentage , in and of itself, is not a hard fast rule in determining how "spready" a diamond is- yet more times than not, lower depth does equal greater spread.

RD,

Without a proper estimation of loss from rounded corners and sides a comparison between round and cushion is meaningless.
Considering that rounded corners and sides can change a surface area -20% from an ideal square the error is too large for any comparison like that to be meaningfull.

-15% faceup size versus a round, 65% depth.

 

[Rockdiamond]

ccl- In the real world ( as opposed to simulations), diamonds that are more shallow generally face up larger.
We have seen exceptions to this rule- but they are just that- exceptions.

 

[ChunkyCushionLover]

ccl- In the real world ( as opposed to simulations), diamonds that are more shallow generally face up larger.
We have seen exceptions to this rule- but they are just that- exceptions.

RD,

How exactly are you calculating they have equivalent faceup size?
Have any proof(like an example) to backup your statement?

 

[antelope1]

OP -- as you can tell from the discussion above -- there are lots of different types of cushions and you might want to look at a few (or a lot) before you decide (a) that you want a cushion, and (2) the type of cushion that you want. Jonathan at GOG has a ton of videos, and you could start with those.

If you decide that you do want a modified/modern/antique/old mine cushion after all, then come back and ask about finding specific types of cushions. You'd probably get a more informative help that way.

Good luck!