Have you ever looked at a gemstone for so long its shape and reflections start to make no sense ?
Make it move just a little and it worsen !
The light we perceive emanating from it seems to go from everywhere and it confuses our brains. To keep a little mental dignity, we call it a “fire” or a “sparkle” or a “scintillation” and then go look at a grey wall to catch a break.
Gemstones are cut so that the overall effect of its different facets can generate different physical effects when interacting with one another going from dispersion (fire) and brilliance (color outlook) and luster (outside shine) to flashes of reflected lights (scintillation). Throughout time, the technique behind gemstone cutting tried to balance the search for the most effect with the stone’s fragilities.
Quirks make uniqueness
Emeralds are curious things. Like most gemstones, their colors present hues and variations depending on where they were mined. Columbian emeralds are supposedly more prone to bluish and yellowish greens, whereas Russian ones seem to present more deep blue tones.
The traces elements that take part in the composition of the stone are responsible for this. The complex alchemy that creates the stone also creates inclusions. Those are the tiny “imperfections” in the beryl crystal that can also lead to breakages of its surface. Indeed, flawless and surface breaking devoid stones are extremely rare, bordering on mythical. Or, they’re man made.
Those quirks and “defaults” are sometimes called their garden (the term used is actually “jardin”, french for garden) and every element of it can be precisely described. Such poesy !
They can define a stone as precisely as giving it a name or identifying its complete composition. In fact, it’s how most emeralds are valued and known by. Basically, landscaping.
One last thing about emeralds is their utter fragility. Though a crystal born under tremendous condition inside the earth mantel, an emerald is as fragile as your regular porcelain teapot (around 7.5 on the Mohs scale). That’s why all of them are always encased in jewels: to protect them. That’s also why traditional lapidary techniques are usually limited to a few shapes, namely step cut (sometimes referred to as “emerald cut”), cabochon, pear or oval.
A pear in a russian garden
Enters the recently (2019) sold in auction emerald, previously part of Catherine the Great (1729-1796) jewelery box. Or her treasure chest? Probably a few rooms in her castle. I must confess a total lack of knowledge in that regard. The empress was known to be fond of jewels and to use them both as ornaments and political statements.
In 1874, the emerald was gifted to the grand duchess Maria Pavlovna of Mecklenburg-Schwerin for her wedding to the grand duke Vladimir Alexandrovitch .
Notice the lozenge looking stone on her pectoral ? It’s part of a brooch. A brooch that encased the 107-carat emerald. The size of the stone makes it rarer even. It seems it went something like this:
Now, you undoubtedly noticed that the 2019 stone and this one are somehow different. One is a rectangle and one is pear shaped.
That’s right. The stone was re-cut by the jeweler Cartier in 1954, dropping from a hefty 107-carat to 76. Sources vary a little, and it’s not clear exactly why it was decided to re-cut the stone. Consensus seem to establish the motivation by the then owner’s wish to get rid of a too prominent inclusion.
Cold sweat and light tricks
From all of the above, you certainly can imagine how nerve racking the re-cut of such an important piece must have been for the lapidary in charge !
Now, you might also wonder why a conservator inquires about such things. Crystals are not, even slightly, something actually restored. It really doesn’t need to be, and to be fair possible actions are quite limited anyway. At best, it is re-positioned and secured with glue and no one is the wiser.
But there is something that 3D can actually help us curate: the transformation of the stone.
Yes. I’m desperate to model sparkly things.
See you in the next part, where we get to grips with the actual task of 3D modeling the stone in its two historical states !