Wednesday, October 7, 2015

Just Add Water

The Queen of Gems, opal is an extraordinary stone that's even more fascinating inside.


Australian Black Opal ring by Ornella Lanuzzi 
They Were the Talk of the Town
Opal, perhaps first called opalus by those clever Romans, was referred to by prolific Roman author Pliny the Elder who lived circa 23-79 AD. The Greeks, fond of claiming most every word as originating from their language also think the word sprang from their opallus, which expresses a form of 'seeing'. 

Kind of Sloshy, Aren't They?
Anyway you look at it, we like seeing precious opals. These forever fascinating stones are indeed original wonders. No two ever look exactly alike. The hydrated silica stones have, you guessed it, loads of hydration  . . or captured water inside. Most precious opal contains between 6 to 10% water by weight. In certain instances, the amount tops 21% water. Imagine that.

And Kind of Pollock-y Too
Their claim to fame is a play-of-color thanks to their unusual internal structure. Composed of silica spheres, they create a closely packed lattice--looking like a bunch of bubbles--albeit nano-bubbles to be sure. This unique structure allows for light to be diffracted all over the place. Before you know it, every color of the rainbow is splashed across one little stone. 


Coober Pedy, S. Australia multi-color crystal opal rough

Here's a pretty good example of the extraordinary color show possible. The opal can present an abstract art-like swath of colors seemingly painted across the surface of the stone. Say thanks to its amorphous (all over the map) crystal system. What a stroke of luck for opal enthusiasts. You'll never see that piece again--and so the collecting frenzy begins.

Don't Try This at Home
If you could peek deep inside a piece of opal through a high powered microscope, and scientists can of course, you'd get another perspective that takes your breath away.


Mexican Opal 23.15 cts observed at 60X magnification: Courtesy Pala Gems


The micro-photo (magnified at 60 times) shown here drives home the point as to just how amorphous (translation: unorganized crystal structure) opal crystals really are. And that's a good thing. The highly irregular internal structure is the cause of the wild spray of who-knows-what colors that dance across the surface of the stone.

Let's All Have a Look at It Now
According to Gemologist Gabriel Mattice, Gemstone Acquisitions and Collections at Pala Gems, the remarkable opal shown here was donated to the Musée National d'Histoire Naturelle in Paris.  

Such a rare natural specimen should be on display for all the world to enjoy, n'cest-pas?

No comments: