The intricacies and risks of diamond-cutting

[Garry H (Cut Nut)]

Date: 4/30/2006 3:55:23 AM
Author: DiaGem

Garry,

According to your knowledge, at what total depth (in a round) in a diamond do you see (visualize) the ''large dark, dull BLACK SPOT in the middle''?

unfortunately hell will freeze over before we have a simple answer DG.

The darkness is caused by too deep (leakage)
And too shallow (observer blocks too much light)

In the deep case / leakage case - a brilliant cut (BIC) border line might be a 60:60 stone - 60 tablle, 30 crown angle slt thk girdle and 42.4 pavilion angle - 60% depth.
In the case of a firey ideal cut - try a 50% table, 38 crown angle, slt thk and 40.4 pavilion angle - this depth is 65.7% and I have no trouble selling these stones (but they are hard to get)

 

[diagem]

Date: 4/30/2006 4:42:30 AM
Author: Garry H (Cut Nut)

Date: 4/30/2006 3:55:23 AM
Author: DiaGem

Garry,

According to your knowledge, at what total depth (in a round) in a diamond do you see (visualize) the ''large dark, dull BLACK SPOT in the middle''?

unfortunately hell will freeze over before we have a simple answer DG.

The darkness is caused by too deep (leakage)
And too shallow (observer blocks too much light)

In the deep case / leakage case - a brilliant cut (BIC) border line might be a 60:60 stone - 60 tablle, 30 crown angle slt thk girdle and 42.4 pavilion angle - 60% depth.
In the case of a firey ideal cut - try a 50% table, 38 crown angle, slt thk and 40.4 pavilion angle - this depth is 65.7% and I have no trouble selling these stones (but they are hard to get)

Garry,

Since i am mostly cutting fancy shaped diamonds, the thing that doesnt make sense, why would a round with a 50% table and 38 deg. crown combined with a 40.4 deg. pavilion be a hard to get stone????

Please explain, maybe i can help you get these...

 

[Garry H (Cut Nut)]

Usually the pavilion is too deep - with this built up crown a shallow pavilion is essential.

Also these goods are treate as second rate and finding excellent symmetry and polish.

 

[diagem]

Date: 4/30/2006 6:58:15 AM
Author: Garry H (Cut Nut)
Usually the pavilion is too deep - with this built up crown a shallow pavilion is essential.

Also these goods are treate as second rate and finding excellent symmetry and polish.

What are the pavilion angle''s that are within the ranges? and what is the maximum crown heights for the to be desirable?

and what do you mean "treate as second rate and finding excellent symmetry and polish"?

 

[Garry H (Cut Nut)]

Date: 4/30/2006 7:34:43 AM
Author: DiaGem

Date: 4/30/2006 6:58:15 AM
Author: Garry H (Cut Nut)
Usually the pavilion is too deep - with this built up crown a shallow pavilion is essential.

Also these goods are treate as second rate and finding excellent symmetry and polish.

What are the pavilion angle''s that are within the ranges? and what is the maximum crown heights for the to be desirable?

and what do you mean ''treate as second rate and finding excellent symmetry and polish''?

The pavilion angle range is listed above and you can see them easily on the HCA charts too DiaGem.

Stones a long way off Tolkowsky proportions are often not polished to such high standards of symmetry and polish

 

[Paul-Antwerp]

Date: 4/29/2006 3:17:18 PM
Author: jasontb
I''m still shocked that Paul needs to be making nearly *perfect* estimates to avoid throwing off his financials.

The reason, why this makes such a big financial difference, is mostly because of the particular area of colour-clarity-combos of this parcel.

There is a huge price-difference, if one goes from G to H-colour, and this is the colour-area of this parcel. In the same way, going from SI1 to SI2, and worse even, some stones to I1, also makes a huge difference, which the few VS''s cannot make up for.

And in the long run, it is a matter of statistics. Next time, we will try to buy the same assortment from the same supplier at a slightly lower price. And on that parcel, the difference in grading will be slightly better than the estimate. Buying rough to cut is a calculated gamble, and sometimes, you do perfect estimates and still run at a loss. The sensible thing to do is continue to rely on your system, and on the next parcel, luck will reward you in the other direction.

It is the gamblers without a system that lose consistently.

Live long,

 

[Garry H (Cut Nut)]

Date: 4/30/2006 12:46:26 PM
Author: Paul-Antwerp

Date: 4/29/2006 3:17:18 PM
Author: jasontb
I''m still shocked that Paul needs to be making nearly *perfect* estimates to avoid throwing off his financials.

The reason, why this makes such a big financial difference, is mostly because of the particular area of colour-clarity-combos of this parcel.

There is a huge price-difference, if one goes from G to H-colour, and this is the colour-area of this parcel. In the same way, going from SI1 to SI2, and worse even, some stones to I1, also makes a huge difference, which the few VS''s cannot make up for.

And in the long run, it is a matter of statistics. Next time, we will try to buy the same assortment from the same supplier at a slightly lower price. And on that parcel, the difference in grading will be slightly better than the estimate. Buying rough to cut is a calculated gamble, and sometimes, you do perfect estimates and still run at a loss. The sensible thing to do is continue to rely on your system, and on the next parcel, luck will reward you in the other direction.

It is the gamblers without a system that lose consistently.

Live long,

I believe you and many other leading Belgian Diamantaires were very impressed with the Helium Rough demo in Rico last week Paul.

do you think it would help mush?
Of course again - you can not go polishing windows on spec rough - which is a big problem for you guys I know.

 

[Paul-Antwerp]

Date: 4/30/2006 7:47:35 PM
Author: Garry H (Cut Nut)

I believe you and many other leading Belgian Diamantaires were very impressed with the Helium Rough demo in Rico last week Paul.

do you think it would help mush?
Of course again - you can not go polishing windows on spec rough - which is a big problem for you guys I know.

I did not get admitted to the club of leading Belgian Diamantaires yet, Garry. And I am not easily impressed, either.

Would it help? I do not think so.

Live long,