EVOLUTION OF THE IDEAL CUT

[strmrdr]

Date: 1/19/2008 3:32:03 AM
Author: strmrdr

Date: 1/19/2008 2:59:22 AM
Author: DiaGem
Strmrdr,

If the above examples had the same girdles, depth and diameter..., which one would weigh more?
The shallow or deep crowned one?

I can get you that answer tomorrow but shallower crowns will yield 2 heavier stones from the same octahedron rough compared too higher crowns.

Thanks too Brian at WF for the graphic he posted in another thread..

 

[diagem]

Date: 1/19/2008 3:32:03 AM
Author: strmrdr

Date: 1/19/2008 2:59:22 AM
Author: DiaGem
Strmrdr,

If the above examples had the same girdles, depth and diameter..., which one would weigh more?
The shallow or deep crowned one?

I can get you that answer tomorrow but shallower crowns will yield 2 heavier stones from the same octahedron rough compared too higher crowns.

The example is: "33/41.4 vs 34.8/40.8 with the same table size."

I would think (because you added "same table size") the latter shallower pavilion with steeper crown would be heavier in weight!
Other wise the shallow crown with the steeper pavilion should weigh more.

But thats just my guess..., the nuances would be micro...

 

[diagem]

Date: 1/19/2008 3:41:48 AM
Author: strmrdr

Date: 1/19/2008 3:32:03 AM
Author: strmrdr

Date: 1/19/2008 2:59:22 AM
Author: DiaGem
Strmrdr,

If the above examples had the same girdles, depth and diameter..., which one would weigh more?
The shallow or deep crowned one?

I can get you that answer tomorrow but shallower crowns will yield 2 heavier stones from the same octahedron rough compared too higher crowns.

Thanks too Brian at WF for the graphic he posted in another thread..

Strmrdr,

Thats not a typical build of an octahedron rough...
Usually they are steeper in depth.

Its true..., you can get 2 heavier Diamonds when their crowns are shallow..., but you can even get 2 heavier Diamonds if you go steep/steep as you will have the room.

 

[Garry H (Cut Nut)]

storm the best yeild for rounds comes from one steep deep main stone and one very shallow crown, big table deep pavilion smaller stone. Rarely do 2 equal sized round stones come from 1 rough (princess do though)

 

[diagem]

Garry, which stone will weigh more?

The example is: The example is: "33/41.4 vs 34.8/40.8 with the same table size."
Same depth, diameter, girdle thickness, and lgf,ugf,stars...

 

[Garry H (Cut Nut)]

Date: 1/19/2008 6:41:13 AM
Author: DiaGem
Garry, which stone will weigh more?

The example is: The example is: ''33/41.4 vs 34.8/40.8 with the same table size.''
Same depth, diameter, girdle thickness, and lgf,ugf,stars...

For a 1ct stone the diamond with the steeper crown weighs 0.013ct more if the table is 57%

I guess if the table is bigger there is less diference and if it is smaller there is more difference

 

[strmrdr]

Date: 1/19/2008 6:22:25 AM
Author: DiaGem
Strmrdr,

Thats not a typical build of an octahedron rough...
Usually they are steeper in depth.

Its true..., you can get 2 heavier Diamonds when their crowns are shallow..., but you can even get 2 heavier Diamonds if you go steep/steep as you will have the room.

then you lose performance if you go steep/deep....
In RB''s wont get ags0 and in 10 fold wont get all red IS images.
steep/deep is not an option in that case

 

[diagem]

Date: 1/19/2008 10:37:35 AM
Author: strmrdr

Date: 1/19/2008 6:22:25 AM
Author: DiaGem
Strmrdr,

Thats not a typical build of an octahedron rough...
Usually they are steeper in depth.

Its true..., you can get 2 heavier Diamonds when their crowns are shallow..., but you can even get 2 heavier Diamonds if you go steep/steep as you will have the room.

then you lose performance if you go steep/deep....
In RB''s wont get ags0 and in 10 fold wont get all red IS images.
steep/deep is not an option in that case

So it doesn''t improve cutters yields as you said previously...

Now..., I dont have any experience in 10 folds..., but common sense tells me that a 10 fold will produce a lower yield stone if cut to same parameters as a 8 fold..., just a guess!

 

[strmrdr]

Date: 1/19/2008 11:14:17 AM
Author: DiaGem

Date: 1/19/2008 10:37:35 AM
Author: strmrdr

Date: 1/19/2008 6:22:25 AM
Author: DiaGem
Strmrdr,

Thats not a typical build of an octahedron rough...
Usually they are steeper in depth.

Its true..., you can get 2 heavier Diamonds when their crowns are shallow..., but you can even get 2 heavier Diamonds if you go steep/steep as you will have the room.

then you lose performance if you go steep/deep....
In RB''s wont get ags0 and in 10 fold wont get all red IS images.
steep/deep is not an option in that case

So it doesn''t improve cutters yields as you said previously...

Now..., I dont have any experience in 10 folds..., but common sense tells me that a 10 fold will produce a lower yield stone if cut to same parameters as a 8 fold..., just a guess!

yes it will improve yeild just not as much as going steep deep...

 

[diagem]

Date: 1/19/2008 11:36:14 AM
Author: strmrdr

Date: 1/19/2008 11:14:17 AM
Author: DiaGem

Date: 1/19/2008 10:37:35 AM
Author: strmrdr

Date: 1/19/2008 6:22:25 AM
Author: DiaGem
Strmrdr,

Thats not a typical build of an octahedron rough...
Usually they are steeper in depth.

Its true..., you can get 2 heavier Diamonds when their crowns are shallow..., but you can even get 2 heavier Diamonds if you go steep/steep as you will have the room.

then you lose performance if you go steep/deep....
In RB''s wont get ags0 and in 10 fold wont get all red IS images.
steep/deep is not an option in that case

So it doesn''t improve cutters yields as you said previously...

Now..., I dont have any experience in 10 folds..., but common sense tells me that a 10 fold will produce a lower yield stone if cut to same parameters as a 8 fold..., just a guess!

yes it will improve yeild just not as much as going steep deep...

Strmrdr..., as an extremely educated Diamond consumer... (and i really mean that!

), which of the new cuts you think made the most impact as an innovative Diamond brand?

 

[strmrdr]

Date: 1/19/2008 11:53:33 AM
Author: DiaGem
Strmrdr..., as an extremely educated Diamond consumer... (and i really mean that!

), which of the new cuts you think made the most impact as an innovative Diamond brand?

none of them are really innovative the cuts have been around for decades in gemstones.
10 fold stones have been cut since the 50s and maybe earlier.
Same with 129 and 88 facets there really isn't much that can be cut from rough that hasn't been tried before.

That said I think the star129 is likely the one with the most market share when judging by how many stores carry them.
3 local stores have them which is more than all the others combined.
On PS the ones with the most impact would be the Solasfera and the Jubilee and Regent.
I think that the Regent made the most impact of the 3 as it created demand for high performance non-princess squares on PS and came out first.
The Jubilee made a bigger splash but the Regent paved the way.

edit: Wanted too add thanks for the compliment :}

 

[michaelgem]

Re your question: Thanks Michael. Does the book give a reason why 8-sided symmetry is so popular in round diamonds? I see there are some 10-sided stones out there which look very good yet have not become popular. The ten-fold symmetry ones might be very strong performers in larger sizes, but it is just an intuitive guess on my part.
David S. Atlas

David, being among the knowledgeable experts on this forum, you likely have as good an answer in mind as any of us. I think you are asking this question to stimulate thought and discussion. And judging by the many good responses from other experts here, you have succeeded. Here is my two cents as indirectly addressed in the Accordance article:

Along the lines of thinking already mentioned, going from 8 to 10-fold symmetry, while retaining similar light performance as measured by some metrics, does reduce the size of the "large flash brilliance and fire" that are the hallmark of the early "Ideal Cuts" from the times of Morse and Tolkowsky. Just as lowering the pavilion half-length from the roughly 60% of Tolkowsky''s era increases the amount of scintillation at the expense of large flash sparkle and fire, so does going from 8 to 10-fold symmetry. I suspect that your intuitive guess that 10-fold symmetry would be great in larger sizes is based upon the understanding that larger sizes compensate for the decrease in the large flash sparkle and fire from more numerous (10 vs. but smaller (% wise) mains.

For usual round brilliant diamond sizes in the range affordable by the great majority of consumers, I think 8-fold symmetry remains the way to go. Keeping the lower half length close to 77% with 8-fold symmetry is in keeping with the belief that "an attractive balance between the areas occupied by the mains and halves in necessary to retain the large flash sparkle and fire of the early Ideal and at the same time provide a greater amount of scintillation."

Switching gears to address matters of popularity or taste:

Although some features of diamond beauty such as lower half-length are often called matters of taste, all the grading systems are based upon the consensus of the taste of one group or another. That is how the boundaries on Ideal proportion combinations are arrived at. Past the parameter boundaries of a particular groups grading system, the consensus of the groups taste is that the diamond''s light performance or beauty is noticeably impaired and no longer Ideal or Excellent.

As far as lower half-length goes, sufficient deviation from the central lower half length of about 77% will take a given proportion combination out of the range considered Ideal or Excellent. In the GIA system a deviation over 7.5% from 77.5% takes a proportion set out of the grade of Excellent. Cutters of Super Ideal cuts keep their lower half length even closer to 77%, between 75% and 80%. For manufacturers of optically symmetric, hearts and arrow diamonds this length is critical and is allowed little deviation.

Even though many aspects of diamond beauty or light performance are matters of taste, the consensus of the taste of the group doing the grading ultimately determines the range or sweet spot considered Ideal or Excellent by that group. This is just to say that beyond certain boundaries determined by each groups grading system, a sufficient parameter deviation ceases to be a matter of taste and drops a diamond proportion set from the ranks of Ideal or Excellent.

Michael D. Cowing FGA

 

[JohnQuixote]

Date: 1/19/2008 12:40:20 AM
Author: Garry H (Cut Nut)

Date: 1/18/2008 11:54:52 PM
Author: JohnQuixote

You're certainly right about daylight Garry but diamonds are not sold there. I really think this adjustment was driven by feedback from merchants in the gradually evolving sales environment: In 1920 electric lights (low-hanging) started coming into use and sellers were just beginning to see the sizzle caused by adjustments. Jewelry store schemes evolved slowly and steadily. More powerful, multiple source spotlighting lent itself to lengthening of the lower halves but that did not happen overnight. Look at the complex schemes we have today. We're far from the first electric light schemes...

Good arguements John
But I am not totally convinced - if the science was really valued, and it really was science, then as GIA Cut Team have said before, the minor facets should be important. Today it is rare to find a stone in the low 70's or high 80%'s. It seems to have evolved that way beginning in the mid 1930's and perhaps over shooting in the late 1960's from my experiential observations (looking at clients diamonds and guessing the date of grannies engagement etc).
I think it was cutters themselves.
I have yet to hear any evidence that scientists or gemologists or even gemmologists were involved. (But i am only 1/2 way thru Al's book).

Garry I’m with you.

I don’t think it was science either. I’m not heavily invested in whether it was eventual gemology or (as I presume) long-term feedback from merchants about what was selling that drove the cutters to change - and also drove jewelry store lighting to become what it has - but I have theories.

Anyway it's Saturday and rather than writing a boring synopsis I composed a boring opera.
You’ll have to imagine dramatic singing.

The Cutter of Seville (Il tagliatore di Siviglia)

* Dramma Musicale *

Personaggi

Cutter (tenore) A humble diamond cutter with an ailing father who lives upstairs
Merchant (basso) Seville’s nefarious sales-baron, versed in arcane tactics and lighting.
Chorus (coro misto) Happy citizens, enchanted by sparkles and beauty.

ACT I Downstairs at the cutter’s house

Cutter: Well met, sir. I have cut you six diamonds anew. Three short lgf, three long.
Merchant: I thank you master Cutter. I depart to sell them now… (exit)
Cutter (to self): While he sells them I shall cut more…

ACT II A brightly lit shop in Seville

Merchant: Ladies, ladies, see my lovely diamonds! Look, I brighten my lights!
Chorus: Oh what lovely diamonds. We like these three best.
Merchant: For you, a special deal today. Only today.
Chorus: Thank you! Thank you!

ACT III The Cutter’s house

Cutter: Welcome my friend, how fare yon diamonds?
Merchant: In sooth, master Cutter, I have sold but three.
Cutter: Then here are six more. Three short lgf, three long.
Merchant: Hold! The long I accept. But not the short.
Cutter: Explain yourself!
Merchant: When I brighten my lights these three will sing.
Chorus (offstage): They sing! They sing!
Cutter: But this lighting is unnatural…
Merchant: And yet they sing.
Chorus (offstage): They sing! They sing!
Merchant: How will you pay your rent?
Cutter: Ach! Take them then. And away with you.
Merchant: As you wish. (exit)
Cutter (to self): Father forgive me. I must pay our rent…

ACT IV The brightly lit shop

Merchant: Ladies, ladies, see my lovely diamonds! See that my lights are even brighter today!
Chorus: Oh what lovely diamonds! So sparkly! So pretty! Again, we like these three best.
Merchant: Again! Again! (to self) I must get brighter lights still…

ACT V The Cutter’s house

Cutter: Aha. There you are. See. I have cut all with long lgf.
Merchant: It is true. I see. But you must make them longer still.
Cutter: What treachery is this!? You do no justice here!
Merchant (hands him money): But see…our vice…has a price…
Cutter: It is against my father’s teaching.
Merchant (more money): He would wish a better life for you.
Cutter: What to do?
Merchant (more money): Ease your pain, my friend. Make the diamonds sing…
Chorus (offstage): They sing! They sing!
Cutter: Ah. What to do?
Merchant: Make these diamonds sing…
Chorus (offstage): They sing! They sing!
Merchant: (leading him to the cutting wheel) Make these diamonds sing…

(cutter begins polishing…fade to black…sound of Merchant laughing)

In Act VI the Merchant is revealed as Mephistopheles from Faust. The Cutter’s father arrives to trade his own soul in exchange for his son’s freedom but it is too late. Suddenly the Cutter, father and Chorus are all struck by a runaway dirigible and perish... This is opera, after all.

Concludere