Ask The Experts FAQ and Ask the experts

[OoohShiny]

As Garry posted in another thread today, which reminded me...:

I suspect the lighting.
Better cuts perform badly in overly spot lit stores and Cartier have typically the worst lighting I have come across.
As Paul noted, D Flawless are very often poorly proportioned and bad cuts appear glassier in spot lighting (and sunlight) than really well cut stones.

...I think we should definitely try to cover "Why do really well-cut stones look dark / bad in strong sunlight?"

 

[Garry H (Cut Nut)]

Search and yee shall find many topics on my diamond looks dark in sunlight.
essentially point light sources in well cut stones may result in one to 3 very bright spots which over expose your eye making the rest of the stone dark.
bad cuts and many fancy shapes with multiple virtual facets can return several or many fairly bright but not dazling rays to your eyes.

 

[OoohShiny]

Sorry, more thoughts on possible questions from me, prompted by various things posted today, including by @Texas Leaguer!

Hopefully easy to answer, though!

So...


re: MMDs / LGDs, there are CVD and HPHT options available.

Am I correct in thinking that both of these growth options will have more organised/regular internal structures than mined diamonds?

And will therefore be easier to cut?

If they are both easier to cut, is one easier than the other?

Aren't they all Type IIa stones? Either way, are all Type IIa stones (natural or grown) easier to cut that other types, because of increased purity meaning a more regular structure??

And on the opposite side of the coin, are all coloured stones more difficult to cut? (I know Yoram has posted about how hard to cut Argyle browns are, for example.)

 

[Texas Leaguer]

My comments about automation and mass production were based more on conjecture than direct knowledge.

It seems logical that because LGD is a very controlled process, that eventually (probably very soon), they will be able to produce very regular, pure material in large sizes and quantities. Competition for production cost advantage will encourage growers to make very consistent roughs that will lend themselves to efficient, high volume processing with robotic cutting.

 

[Texas Leaguer]

Not sure how they are making the colors. I think most natural pinks owe their color to 'plastic deformation' of the crystal lattice. That could certainly present challenges to cutting. LGD pinks may be colored by a different process. It would be interesting to learn more.

 

[Paul-Antwerp]

I think that the difficulties of the crystallisation-process in producing synthetic diamonds are underestimated. It is no coincidence that the number of producers actually producing bigger sizes (as opposed to 0.01 Ct. and smaller) is still very low.

As far as the HPHT-process goes, the bigger a rough crystal becomes, the more difficult it becomes to keep the necessary pressure and temperature (P and T in the abbreviation), which makes the crystallisation-process more difficult. This affects clarity and hampers useful further growth.

And in the CVD-process, one of the tricks in getting thicker material results in the cutting of that rough becoming far more difficult.

Do remember, jewelry use is only a temporary step for the producers of synthetic diamonds. The final goal is industrial use, for many purposes.

Live long,

 

[Garry H (Cut Nut)]

Not sure how they are making the colors. I think most natural pinks owe their color to 'plastic deformation' of the crystal lattice. That could certainly present challenges to cutting. LGD pinks may be colored by a different process. It would be interesting to learn more.

Bryan this was in Jim Shigley GIA Vegas presentation