The Rare Gem Series: Black Opal

Imagination time! Put yourself in the stirrups of a Pony Express rider galloping across the Northern Nevada high desert. You stop at a creek in a pristine oasis known as Virgin Valley to give your horse a drink when you glance down to see an iridescent, magical, alien stone that must have come from space laying on the ground.  Curious, and somewhat confused and scared, you pick it up and feel the weight of it in your hands.  The stone is dark and smooth, and as you turn it in your hand it plays with the light.  Fires of bright colors flash and disappear.  Entire rainbows sear their spectrum into your brain.  You lose track of your objective and why you’re here.  This amazing stone has hypnotized you.  You are lost with out it.  Your past no longer exits.  You cannot envision a future without it.  It’s possession is your everything. It is your precious.

This is was how the black opal was discovered.

That’s a lie.  This is the myth created by the Nevada Tourism Board of how the black opal was discovered.  The truth is that the Pony Express followed the routes of the Oregon trail far to the North and the California Trail far to the South.  Also, the Pony Express only lasted 18 months, from April 3, 1860 – October 24, 1861.  In reality it was probably some ranch hand, or ranch rider that discovered the first black opal about forty years later in 1900, and his response was probably more along the lines of, “What the fuck is that?”

"What the fuck is that?" image from goldnuggetwebs.com
“What the fuck is that?” image from goldnuggetwebs.com

Lightning Ridge, Australia has a more gruesome beginning.  The town in New South Wales near the border with Queensland got its name in the 1870s when some passersby discovered the bodies of a rancher, his dog, and some 600 sheep all of whose hearts had basically exploded from being struck by lighting.  That’s something to put on the old “move here” brochure to promote your town; except that is also probably a lie, but a badass one at least.

Halfway across the world from Virgin Valley, in 1902, Charles Waterhouse Nettleton, a struggling opal miner from White Cliffs in Eastern New South Wales, migrated North into Queensland in search of his own strike.  He struck out.  Pretty much like he had every other time he tried his hand at prospecting.  Nettleton, defeated but ever the optimist, and since he was a stoic, kept on chuggin’ along.  He decided to walk the 400 miles back to White Cliffs, and on his way back Nettleton stopped off in Lightning Ridge and camped with the Ryan family .  The family showed him some freaky black stones that flashed color.  Nettleton recognized them as opals, but like nothing he had ever seen.

With nothing else to do (or lose) Nettleton gave a shrug and dug a big hole.  He set up camp and sunk his first shaft on October 15th, 1902.  Yeah, Nettle didn’t find shit.  Again.  Not to be deterred, Nettleton moved his camp and sunk a second shaft in 1903 and struck pay dirt.  Tens of pounds of the crazy black stones ranging from a carat to a hundred carats in size came tumbling out of the walls of Nettleton’s mine.  The hill where he made his strike is known as Nettleton Hill today.  Excited from his success Nettleton made his way to Sydney (over 350 miles by foot!) to show the stones to a jewel dealer who was not as impressed with them as Nettleton was, and only offered $1 for the lot.  “Well, fuck that,” said Nettleton, and in November 1903 Nettleton walked back to White Cliffs (remember, this is another 503 miles BY FOOT) where he knew there were people who where knowledgeable and could give a good price for his opals; unlike that dickweed, suit-and-tie pissant in Sydney.  On November 11th, 1903 an opal merchant in town offered him $30 bucks for his lot. “Oh hells yeah!” said Nettleton (or whatever the backwoods, Australian-hick equivalent would be) and sold them right there.  Think about this, Nettleton was a brute; he had dug several giant mine shafts (by hand), walked over 1,800 miles, and for his two years worth pain and struggle was psyched to be given $30 for his life’s work.  Stoics, what would this world be without them?

The connection had been made.  The opal dealer started sending his partners to Lightning Ridge to purchase large quantities of the stones.  The rush was on.  Nettleton was a hero.

A beautiful full-spectrum harlequin black opal from Richard W. Wise at rwwise.com
A beautiful full-spectrum harlequin black opal from Richard W. Wise at rwwise.com

By this time Australia had already become the opal capitol of the world with strikes in White Cliffs, and the boulder opals of Queensland.  It didn’t hurt that Queen Victoria loved the stone, and soon after Nettleton’s first rich strike in Lightning Ridge opals were discovered in Andamooka, and Coober Pedy, Koroit, and Minitabie.  While these stones are beautiful, nothing except the stones from Virgin Valley, NV and Lightning Ridge were truly black bodied.

The first big mines opened in Virgin Valley in 1905.  The first big mines opened in Lightning Ridge in 1905.  The rock that forms the area around Lightning Ridge is sandstone from the early Cretaceous Period that formed a shallow sea.  Not only are there opals there but important fossils dating back some 110 million years… Then again, the opals are fossils themselves.

What’s that?

Oh yes, opals are fossils.  What happened was that there was a volcanic eruption from somewhere nearby that coated the area in silica-rich ash.  If a creature or a plant kicked the bucket while in a puddle of water and got coated with ash, the water and ash worked together to preserve the dead critter/plant.  Over millions of years (likely) the silica combined with the water to replace the cellular structure of the organism with opal.  Opal is just a combination of water and silica creatively known as “hydrated silica”.  SiO2 is quartz, SiO2nH2O is opal.  Volcanoes pump out silica during an explosive eruption, if that silica ash buries something wet there is a good chance opal may form.  The water content of the black opals from Lightning Ridge is about 5% making them not likely to craze or crack when unearthed from drying out.

In Virgin Valley it is a different story.  Around 16 million years ago there was a series of volcanic eruptions of rhyolite that lasted for darn near two million years.  These eruptions spit out all sorts of silica-rich ash and the volcanic rock formed a series of hills that encircled an ancient basin that geologists named Canyon Rhyolite.  These volcanic eruptions are no joke.  Once the mountain goes *boom* a superheated blast of air and ash can travel across the region at hundreds of miles per hour killing everything in its path.  Combine this with a few hundred feet of ash covering the Earth around the volcano, and nothing survives.  Nothing.

Canyon Rhyolite, since it was a basin, held a series of lakes and ponds where critters flourished in a rich forest dense with ginkgo, sequoia, spruce, hemlock, birch, cedar, larch and chestnut.  The region was spared from major volcanic events for about four million years when a jerk of a hotspot decided to flood almost the entire region of what is today the Northwestern United States with flood basalt.  This buried Canyon Rhyolite under a dense, solid layer of lava that solidified above it.  Over the course of the last ten million years hot springs began to bubble up through the Earth yearning to break free.  With the hot trickles of water came bits of that silica-rich ash that permeated the buried remains of the lush forests of the now vanished canyon.  What did we just learn about the combination of silica and water?  You guessed it; opals!

The hot spring squirted through the basalt and started dribbling downhill.  Today that hot spring has carved quite the path and formed what is we know today as Virgin Valley.  Along the Valley’s walls, at about the 5090ft level you will find a layer of moist gray clay.  This marks the floor of the ancient forest.  The clay layer may vary from a few inches to a few feet thick, but here is where you will find your opals.  Petrified wood, opalized tree limbs, even the teeth and skeletons of forest creatures preserved forever as majestic hunks of gemstone.  A pretty noble way to go if you ask me.

When I die, I want someone to lay my carcass down in a bog next to an erupting volcano so that maybe, someday, several million years from now I can be dug up and brutally bandsawed and then ground down and polished into ornamental pieces of jewelry for some rich housewife.  A boy can dream can’t he?

The problem faced with many of these Virgin Valley opals is their extremely high water content of 20%; much higher than that of their Australian counterparts.  This makes many opals gorgeous but notoriously unstable.  When these opals are unearthed the majority are placed into containers of water to keep them from drying out.  When an opal dries out it crazes (forms cracks), will loose it’s dark color, and quite often will explode!  Some apply sealants to the stones to retain their water content, some just roll the dice and dry them out and hope for the best, but most just keep them submerged.  While it would be awesome to have a nice large, dry Virgin Valley opal, putting a $100,000 stone in the sun in hopes of it not exploding or just fading into a $10 rock takes some serious balls.

A Virgin Valley black opal being preserved in water. nevada-outback-gems.com
A Virgin Valley black opal being preserved in water. nevada-outback-gems.com

Throughout Ethiopia new opal fields are being discovered almost every year.  These precious opals may have white or blue bodies, and some even chocolate, but the black bodied opals resembling those of Virgin Valley or Lightning Ridge haven’t materialized in the numbers hoped for, or possibly at all!  That doesn’t mean they haven’t been sold.  A process known as “smoking” is putting lower quality crystal opals into the market and trying to pass them off as the elite black opals.  Essentially, the tricksters are taking normal light bodied stones and “smoking” them until the soot permeates the interior of the stone’s matrix.  To the common eye they look amazing, but in the long run, the stones are more likely to crack, pit and fade than the real deal.  Just don’t pay a bunch of money for a black Ethiopian opal just yet.

Other black opals discoveries have reportedly been make in Indonesia (but some of those stones have been “smoked”); with two recent discoveries in central Wyoming, and along the North Fork of the Snoqualmie River in Washington State!  With the incredible ash fallout that originates from hotspot volcanoes like the Yellowstone Caldera and the Long Valley Complex in California I would surmise that there are thousands of undiscovered sites for precious and black opal from Wyoming through Colorado and Nebraska; and in California, Arizona, and Mexico.  Get hunting!

I know, you just read a ton of words and all you want to know is, “what are they worth?” Fine.  A precious black opal with small blue/green shifts in color covering about 50% of the stone will get you about $200 per carat.  The more of the stone that is iridescent, and the larger the color flashes are, and the more of a red/green shift those stones have the more money they are worth.  A stone that is 90-100% covered in red/green flashes, with a black body, can expect to sell for upwards of $5,000 to $10,000 per carat.  These are among the rarest fine quality stones in the world, so keep your eyes out for fakes!  Fakes may include treated or smoked stones; doublets and triplets (stones that have a thin veneer of actual opal glued to the outside of an otherwise boring stone); as well a created matrix opals (stones that are the shavings and cuttings of larger opals that are then glued together using resin); and synthetic stones that are made of weird space-aged polymers and shit.  Just don’t get screwed.

Some helpful guides from OpalAuctions.com:

Black Opal Grading Chart from opalauctions.com
Black Opal Grading Chart from opalauctions.com
Types of black opal from opalauctions.com
Types of black opal from opalauctions.com
opalauctions.com
opalauctions.com
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