Old cuts - questions..

[arjunajane]

I have become intrigued by old cut diamonds, and just have a couple of questions..

What is it that causes the black sections in OMC/antique cushions such as in the following pics..? (pls excuse me for not being able to give photo credits, these have been just collected along the way)

Is this dependant on the cut, or is up to the lighting/way the stone is set? Is there a way to avoid a stone that exhibits large black sections based on any parameters?

Also, once set will an OMC have the same "flower pattern" that shows in OEC's and transitional cuts, or will it perform more like a cushion..?

Here are some pics to explain what I'm referring to, (first pic credit to SG's gorgeous ring).

[ Admin - Edited image at the request of image owner ]
Finally, seeing as transitional cuts are harder to come by, would one be "sacrificing" anything by going with an OEC, or is this one of those personal preference type things, lol..?

Thanks in advance for anyone who can answer,
Cheers AJ.

 

[arjunajane]

My apologies, my other two pics didn''t show..

here is the one from the first question

 

[arjunajane]

And another example for the 2nd question,

thanks !

 

[Garry H (Cut Nut)]

Head obstruction - or in this case the black camera lens.
http://www.ideal-scope.com/newsletters_issue004.asp read all about it.

When it becomes very obvious and a negative, then we call it a dark zone. When there is adjacent leakage, then it is not nice

 

[arjunajane]

Date: 9/1/2008 8:50:20 AM
Author: Garry H (Cut Nut)
Head obstruction - or in this case the black camera lens.
http://www.ideal-scope.com/newsletters_issue004.asp read all about it.

When it becomes very obvious and a negative, then we call it a dark zone. When there is adjacent leakage, then it is not nice

Ta for the answer Garry - so, is it just inevitable due to the way OMC''s are cut? As in, is there something I can look for that will make them less succeptible to head obstruction?
Sorry if its obvious and I''m just being daft !

 

[diagem]

Date: 9/1/2008 9:48:37 AM
Author: arjunajane

Date: 9/1/2008 8:50:20 AM
Author: Garry H (Cut Nut)
Head obstruction - or in this case the black camera lens.
http://www.ideal-scope.com/newsletters_issue004.asp read all about it.

When it becomes very obvious and a negative, then we call it a dark zone. When there is adjacent leakage, then it is not nice

Ta for the answer Garry - so, is it just inevitable due to the way OMC''s are cut? As in, is there something I can look for that will make them less succeptible to head obstruction?
Sorry if its obvious and I''m just being daft !

Distance....

 

[Ellen]

Date: 9/1/2008 8:23:29 AM
Author:arjunajane

Also, once set will an OMC have the same ''flower pattern'' that shows in OEC''s and transitional cuts, or will it perform more like a cushion..?

Hey aj, I have an OMC I inherited early, and to me its performance is kind of like a cross between a cushion and a round. It''s not as flashy as my round, but still very pretty. They are actually a cushion cut.

Here''s a pic and the link if you''d like to see it. There''s pics throughout.

Are you thinking of buying one?

One of my faves. And linky.

 

[ericad]

Ok, 1st pic is ours, 2nd is surfgirl's, 3rd is our stone but new owner's pic (Snooper's LM solitaire) and 4th also ours

The first is an early OEC, K color with no fluor, very uber-chunky, and the dark areas mainly visible in pics, but far less so in real life because the stone is picking up the black of my camera. IRL, the center of the stone is a bit darker, and the later OEC is truly a more brilliantly cut stone, but the early OEC is much more firey. I have noticed this dark central area is more pronounced in the older of the old cuts (cushion/OMC and early OECs). The 4th is a later OEC, M/N color, mild blue fluor.

But I would caution you to never make sweeping generalizations about old cuts - it's possible to find OMC/cushions that do not exhibit a "maltese cross" or "windmill" in the center, just as it's possible to find OECs and transitionals with dark spots or appearance that is less pleasing to your eye. Like culets, there are many who love the look of the darker reflections and those who don't. No particular cut will guarantee the flower facet pattern you seek - each stone must be evaluated individually.

My advice is to find a vendor who will listen to what you like in a stone, make a recommendation, and allow you a reasonable inspection period to view the diamond in person and return if it doesn't suit you.

Here's a pic of #1 and #4 next to each other (#4 on the left and #1 after it was reset in a new setting by the owner):

 

[ericad]

Resized to be less tiny!

 

[Upgradable]

Erica is the master! Not only does she have the knowledge, but she has the goods to show you solid examples!! Oh, I would love to live in her closet!!

As to the phenomenon, it is a manifestation of the way the pavilion facets are cut, but there is no way to evaluate it except with your eyes.

 

[diagem]

The flower facet patterns greatly depend on the lgf''s vs. table size combination....

 

[strmrdr]

Date: 9/1/2008 8:50:20 AM
Author: Garry H (Cut Nut)
Head obstruction - or in this case the black camera lens.

http://www.ideal-scope.com/newsletters_issue004.asp read all about it.


When it becomes very obvious and a negative, then we call it a dark zone. When there is adjacent leakage, then it is not nice

combined with large virtual facets


http://journal.pricescope.com/Articles/61/1/Virtual-Facets-and-patterns%2c-a-Discussion-about-step-cuts-.aspx

oec''s do everything big they flash big, they show big obstruction and when they leak they leak big.
That''s the trade off and like asschers you have to love the pattern if its the stone for you.
What you get is awesome low/soft light performance and huge chunks of fire and a ton of large movement scintillation.
The small movement scintillation is also down a bit.

 

[strmrdr]

Here are the virtual facets of an actual oec(left) vs the virtual facets of a tolk. RB.

 

[strmrdr]

This is the upside your trading for, large chunky fire.

 

[strmrdr]

This is what you have to love to get it.
Large contrast zones compared to a RB.

 

[strmrdr]

Here are the virtual facets outlined in dark blue and the crown actual facets in light blue.

 

[strmrdr]

Here is a real world picture showing large contrast patterns.

 

[Upgradable]

clappy clappy storm!!

 

[ericad]

Whoa...cool

Another pic showing a real life example of contrast zones, I think. This was a 3.7ct I/J OEC.

 

[diagem]

1n the contrast you clearly notice the "flower facet patern" due to its lgf''s....

 

[strmrdr]

Date: 9/1/2008 4:58:39 PM
Author: ericad
Whoa...cool


Another pic showing a real life example of contrast zones, I think. This was a 3.7ct I/J OEC.

yep large contrast zones.
Can you take a picture of it or one like it at a greater distance?
Say at least 4 feet.

edit: if you use a different one please provide a close up shot of it also.

 

[ericad]

Hmmm, nope, not able to take any additional pics of that one. I will be taking delivery of this one on Saturday and can do a proper photoshoot over the weekend with your instructions. This cushion also has strong contrast zones.

 

[dani13]

Ohh...that stone is GORGEOUS, Erica!!! Do you know the stats on it? I am just loving these older cuts!!! Hopefully, I will be doing business with you some day!!!

 

[ericad]

It''s a 2.64ct cushion, I/J color, eye-clean SI2. It has since been separated from this vintage mounting, which is lovely but did nothing for the stone''s rectangular cushion shape! It''s a very white stone with distinct dark reflection area that will work nicely for whatever strm has in store for us!

 

[ericad]

one more of the loose stone, for better idea of shape, faceting and contrast zones

 

[dani13]

Oh, I love it!!!!

 

[Snooper]

Interesting thread!

Although the pic of my ring shows a strong maltese cross, it''s very VERY subtle in person. Thanks again Ericad!!!

 

[glitterata]

This thread inspired me to do a photo shoot of my three diamond rings: a 1.4ish ct transition cut from the late 1920s (left), a 1.6iss OEC from the late 1910s (center), and a .73 ct round brilliant cut by Infinity from this year (right).

 

[glitterata]

A larger picture of the OEC, which is a K/L color and SI2 (the inclusion is hidden by a prong):

 

[glitterata]

A closer pictuer of the transition cut, which is F VS2 (because of a little chip or perhaps a natural on the girdle). I'm always surprised to see the arrows in this diamond. It has a rather bad idealscope image, lots of leakage at the edges.