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Opals: The Wet Rock

Opals are not your grandmother’s stones. OK, maybe they are, but they are freaks, freaks of geology, I tell you! I mean did you know that they’re not even really minerals ““ they’re mineraloids. And that’s not everything. To put it simply, John Waters described his work as speaking to “minorities who can’t even fit in with their own minorities.” Opals are perfect for John Waters.

Opal jewel, uploaded to wikicommons by user Gryffindor.

Opals seem simple enough ““ these milky white oval silica stones that sparkle with every color of the rainbow found their way into illustrious company by becoming October’s birthstone. But they’re not quite what they seem. Like I mentioned earlier, opals are not minerals; they’re mineraloids. This means that while they have some properties of minerals, when you get down to their molecules, they do not have the stable, solid structure that makes a mineral a mineral; they are amorphous.

Opals do have some internal structure: the silica that makes up the opal is stacked in tightly packed planes. It’s this structure that gives opals their fire and flashes of color, or play of color, if you want to get technical about it. This play of color is what distinguishes precious opals from common ones (aka “potch” ““ how cool is that word): gemstones know that flashy = fancy.

But for all their pretty colors, opals are fragile stones. They are one of the softest precious stones out there, making them vulnerable to scratches and breaking. The crystal structure (or lack thereof) contributes to the fragility, but opals have another factor weighing in against them: water. See, opals are hydrated silica, meaning that each opal is about 6-10% water. Without proper use and storage, opals can dry out and crack. They can also react very, very badly to freezing temperatures. (Finally! A stone after my own heart”¦wait, I don’t have a heart of stone, I swear.) Opal jewelry must be treated with care, and opals are not ideal stones for everyday wear ““ especially if you plan to wear them on parts of your body (like hands) that might smash into things on a regular basis (looking at you, anything that’s near me when I’m telling a particularly hand-wavy story).

When purchasing an opal, keep the limitations of the soft stone in mind. Also, be aware that opals aren’t always as solidly opal as they seem. In order to emphasize the play of color and the brilliance of the opal, some jewelers will place a layer of opal over a darker rock, like basalt. This is called an “opal doublet.” Sometimes, jewelers will go a step further and place a plastic or clear quartz dome over the opal doublet, making an “opal triplet.” This quartz/plastic dome is intended to protect the opal from damage and is usually only used for poor quality stones.

Boulder opal carved in the shape of a walrus, uploaded to wikicommons by user Arpingstone.

Opals of all quality can form basically anywhere on earth: while 95% (or so) of the world’s opals come from Australia, opals are found all over. Sometimes, the stones are identified by place, but most often, they are identified by color and/or type. Black opals(which aren’t necessarily black, just dark in color) are more rare than white ones. Fire opals are rare, too, but they lack the colorful rainbows and instead are an intense red-orange. They’re all pretty cool, but my absolutely most favorite type of opal is a boulder opal, where you see the veins of opal coursing through a rock. It adds just enough sparkle while reminding me exactly where it came from.

2 replies on “Opals: The Wet Rock”

THANKS for posting pictures with this one!

Although I know all about opals already. I was absolutely fascinated with them after reading Victoria Holt’s book “The Pride of the Peacock” where they move to Australia and own opal mines and the girl gets all interested in it and has great success in the sorting room. But they’re all obsessed with one opal called “The Green Flash at Sunset” because obviously that’s a great name for a stone. And it flashes green, in a sort of sunset-y background.

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