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More Blue, Less Provenance

By Michael Cowing & Robert Long

The entire gem world is reacting to rumors of imminent recutting of the famous Wittelsbach diamond by its new owner Laurence Graf as if this gem’s survival in its current form were as important as the survival of the spotted owl or snow leopard. Leave this historic treasure alone, urged the writers of an article on this diamond in the Winter 2008 issue of Gems & Gemology. And we can certainly understand their pleas for a hands-off policy to the stone’s future.

The Wittelsbach, writes diamond historian Herbert Tillander, is “one of the earliest known Brilliant Cuts,” dating back to at least 1667 when it is believed to have been part of the dowry of the Spanish Infanta, Margareta Teresa, when she married Emperor Leopold. The stone is thought to have been recut in that time frame in Paris, then the world’s most famous and fashion-forward center for diamond refashioning.

One thing for sure: the stone was faceted by a master of the art. An examination of the placement and balance of the unique split facet arrangement on both crown and pavilion shows extraordinary skill, especially given the crude technology of the time. Indeed, we would say that the cutter had brilliandeering skill as good as any we might see today.

Scaled photographs of the Wittelsbach Blue.

Fixing the hole
Nevertheless, many are tempted to castigate the cutter because the stone has a huge ‘hole’ in the center and resembles a life saver. Not so fast. Such ‘holes’ were not then considered the eye sores they are today. And, besides, it is clear the stone was cut from a shallow, tabular-shaped rough whose culet was one of its growth planes. Therefore the decision to leave it pretty much intact and let it serve as a kind of parallel base, or stand, for the even larger table makes good facet design sense. For nearly 350 years, the Wittelsbach’s contrasting outer ring of deep grayish-blue and inner hub of transparency have given the stone its particular esthetic identity.

Hence we say, leave well enough alone. The Wittelsbach isn’t just a relic or artifact; it is the most unique and exemplary piece of craftsmanship from an early time in the evolution of brilliant cutting.

Yet we can fully understand Mr. Graf’s curiosity to know what the impact of recutting might be. Thankfully, there is a way he can have his cake and eat it, too. How? Advanced cutting software allows the cutting of a virtual Wittelsbach to any set of proportions enabling him to see at a glance what the impact will be on color and brilliance. That’s just what we did. Here’s how:

Closing the culet
First, we took measurements from photographs of the three views—top, side and bottom—of the stone (1) along with published measurements of the stone as recorded during several examinations including GIA’s. This data was input to GemCad for Windows, gem faceting software developed by Robert Strickland. Utilizing solid geometry, Robert Long merged the three views into a composite whole employing GemCad to facet a virtual model of the Wittlesbach. (2)

1. Virtual faceting of the Wittelsbach Blue.

Once we had the virtual model of our Wittelsbach, Michael Cowing made photorealistic 3D simulations of it using DiamCalc. (3) This formidable Russian software lets you create stunningly life-like animations of diamonds as they would appear under any lighting circumstance. What’s more, recent additions to this program allow you to create colored diamonds with life-like color, tone and saturation.

2. Photorealistic DiamCalc simulation of the Wittelsbach Blue.

Next, Cowing developed a recut scenario for the Wittelsbach. To sacrifice the least weight, he closed the culet into a keel line, sacrificing 3.08 carats in the process and taking the stone from 36.56 to 33.48 carats (4). This 8 ½ per cent weight drop eliminated the “hole” and gave the diamond’s crown uniform color (5). Is that a plus? No, because it’s outweighed by a mighty minus.

Alas, brilliance improvement achieved by closing of the culet destroys the Wittelsbach’s provenance. This diamond isn’t simply a piece of history; it is a masterpiece that should be left as such.

An animation of the transformation can be viewed here.

3. Virtual re-faceting of the pavilion to close the culet of the Wittelsbach Blue.

4. Photorealistic DiamCalc simulation of the recut Wittelsbach Blue.

Drawing a line
Despite its status as a masterpiece, the Wittelsbach may be a candidate for slight tinkering. The stone has some noticeable abrasions around its knife-edge girdle. One of them even seems to suggest a setting mishap. To give the stone a physical perfection, some suggest removing these abrasions. Like the closing of the culet facet, the result would be “a loss of the stones original substance, identity, and historic form”, as the German historians stated in Gems & Gemology. That’s why we refrained from repairing these slight disfigurements on our virtual Wittelsbach, re-faceting only the pavilion to produce uniform brilliance with minimum weight loss.

Our objective in creating a cyber stone was to give those who fantasized about color improvements a chance to indulge those fantasies. But it was never our intention to advocate recutting of the stone—no matter the results of our exercise in virtual faceting and 3-D photorealistic modeling. The real Wittelsbach is a legendary diamond featuring superb faceting that needs preservation not restoration.

Mr. Graf, are you listening?

Michael D Cowing Gemologist, Appraiser, Research Engineer, AGA Certified Gemological Laboratory
Mr. Cowing is a specialist in facet-design optimization theory and principles of gemstone light-performance.

Robert Long
Mr. Long is a pioneer in modern facet design and cutting techniques, as well as co-author of the innovative “Facet Design” books, the first publications to give exact mathematically derived cutting instructions.

GemCad for Windows is available from:
http://www.gemcad.com/windownload.html

DiamCalc is available from:
http://www.octonus.com/oct/products/3dcalc/standard/

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