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
“What the fuck is that?” image from

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

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.
A Virgin Valley black opal being preserved in water.

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

Black Opal Grading Chart from
Black Opal Grading Chart from
Types of black opal from
Types of black opal from

The Rare Gem Series: Alexandrite

Once upon a time in Russia… Some dudes found a rock and named it after the crown prince since it was his birthday.

The end.

No wait, I mean: The Beginning.

A 1.29ct Russian Alexandrite, Tino Hammid Photography, Inc
A 1.29 carat Russian Alexandrite.

One day in the Summer of 1830 Finnish mineralogist Nils Gustaf Nordenskiöld (1792–1866) was sitting in his office at the Mining Board in Helsingfors when he received a parcel to examine.  Nils was pretty much the most renowned mineralogist of his day so shiny hunks of dirt got sent to him all the time.  No biggie.

Upon opening the contents of the parcel Nils said, “Green, transparent, shiny… Emerald” (or more accurately: “vihreä, tranparant, kiiltävä … smaragdi“), and almost didn’t conduct any further tests; but something just wasn’t sitting right with him.  He began to poke, scratch, smash, and do all the things a good mineralogist does with Earthly byproducts, and he couldn’t get over the fact that the stone was just too hard and not brittle enough to be an emerald.  Weird.

After fussing with it for a while Nils lost the sunlight so he grabbed some dinner and pondered this strange stone while he pushed peas around his plate.  Being a good scientist he abandoned his meal and returned to the lab to inspect the stone under candlelight.  “Mitä vittua?!” Nils half exclaimed/half asked.  The stone, which a few hours earlier had been deep green, was now a rich red!  The next morning the stone was no longer red and had returned to its former deep green!  “Voi Luoja!”

This was no emerald.

The package with the strange stone had come from Count Lev Aleksevich von Perovski (1792-1856) who at the time was trying to climb the social ladder as the royal mineralogist for Tsar Nicholas I of Russia.  Perovski had also identified the stone as an emerald, but the problem was that he kind of sucked at his job, so he sent a specimen to Nils to double check his “work”.

Earlier that Summer Perovski’s team had been poking around in the Izumrudnye Kopi (Emerald mines) in the Ural Mountains (you remember the Urals, that is where Demantoid Garnets were discovered as told via the previous Rare Gem Series post: when they discovered the stones in an alluvial deposit (think gravel river bed) along the Tokovaya River.  By 1831 Perovski had opened his new “emerald” mine and was in full whipping peasants mode to dig faster when Nils sent him a message:

“This ain’t no emerald, genius.  It’s a color-change chrysoberyl and I am calling it  ‘diaphanite‘ which is Greek for ‘something your small brain cannot comprehend’.”

I paraphrase, of course.

Perovski, ever the ladder climber, had other plans in mind.  He wanted to ingratiate himself further with the royal family, Perovski spun a tale that he had discovered it April 17, 1834, the sixteenth birthday of the crown prince and heir to the throne Alexander II, and named it “Alexandrite” in his honor.

Perovski didn’t know how to be a very good scientist, but he knew how to play the game like a champ.  His ploy was well received and he got his ass ingratiated into the royal family like no body’s business; creating the Russian Geographical Society in 1845 and being named the Minister of Internal Affairs, and later the Vice President of the Appanage Department by Tsar Nicholas I (basically, he became the dude in charge of the imperial family’s estates, investments, personal property, and income).  This fancy post also meant that Perovski was in charge of the jeweled trinkets and souvenirs the imperial lapists and jewelers created as rewards for the Tsar’s subjects.

Perovski was a greedy piece of crap.  He used his position of power to threaten, bribe and steal the best stones for the Appanage collection which often found their ways into his own personal collection.  One of Perovski’s underlings, Yakov Kokovin, the director of the Ekaterinburg lapidary, stole an amazing Ural emerald and was caught by Perovski and was braought to trail and later was “compelled” to commit suicide in the dreadful Ekaterinburg Prison.  When Perovski finally kicked the bucket in 1856, the stone, which had now become known as the “Kokovin Emerald”, was found in Perovski’s personal collection. Dick.

Alexandrite quickly became one of the most desirable gem stones in the world. Many sources I have read claim that this is because red and green were the primary colors on the Russian Imperial Flag.  Well, considering that the Imperial Flag was red white and blue, this “fact” is bullshit.  It became popular because it is a rad stone that CHANGES FREAKING COLOR!  Imagine yourself a rich asshole living in Feudal Europe:  you have a fancy house, you have some books, you have a really comfy chair, you have candelabras, you have… well, that is pretty much it.  Some other rich asshole comes along and shows you his new ring that is green during the day and red at night.  “Holy shit!” You’d yell out, “I’ve got to get me one of those, especially since the invention of television won’t happen for another 90 years!”

A beautiful example of a natural Alexandrite in matrix
A beautiful example of a natural Alexandrite in matrix, from Kevin Ward at Exceptional Minerals

By the beginning of the 20th century Russia had pretty much gobbled up all of the Alexandrites in the Urals.  There has been no significant deposits of Alexandrite discovered in Mother Russia since the 1917 revolution.  To this day the best red/green specimens are Russian stones.  They are also the most valuable.

As mentioned above, Alexandrites are a form of chrysoberyl.  While chrysoberyls contain beryllium, they are not related to beryls (emeralds, aquamarine, Bixbite, Morganite, etc…)…  Only sort of-ish, I guess.  Here’s how I would describe the stone as if I were the beaten, over-qualified interpretive guide of the hypothetical “Chrysoberyl Museum” leading a group of tourists in flip flops and aloha shirts:

Leading the tour group into the great hall of the museum: “Chrysoberyls are different from beryls mainly because of their crystal structure.  Beryls are silicates that have big molecules and chrysoberyls only have one beryllium atom so there is less crap glommed onto the beryl atom.  Chrysoberyls only form in pegmatites–“

“But so do Beryls!” Says some interrupting know it all eight year old.

“Shut up, not all of them do!” Says the pissed off tour guide, “Some beryls form in rhyolites. Ha! Now shut your yap and let me do my damned job!”

“What’s a pegmatite?” Asks some oafish dad dragging his bored children along (noses buried in their cell phones).

“Well, that’s a stupid question,” replies the guide (the know it all eight year old nods his head in agreement), “Especially considering that there isn’t a geologist alive that can accurately describe it to you without sounding like a child explaining the story line to “Syriana”.  The facts: a pegmatite is an igneous rock (meaning that it was once molten magma goo that formed far beneath the crust); it created big crystals in its matrix as it cooled; the stuff inside those crystals is similar to that of granite (you know, the kitchen counters in the homes of yuppies); and for geologists it’s like porn, you know it when you see it.  Does that help?”


“Whatever.  Moving on.  When this magma comes oozing up deep from the mantle, it can begin to gather up a bunch of ground water as it moves higher through the Earth’s crust.  The magma is too hot to allow the now super-heated water to join into the formation of any crystals inside the magma.  By the time the magma had mostly cooled, the trapped water formed chrysoberyl in the cracks and crevices out of bits of beryllium and aluminum.  Basically, if it wasn’t for the water being present in the magma, the oxide that is chrysoberyl could not find the oxygen needed to form in the first place!  All you need to make Alexandrite from here is some chromium and your set!  Pretty bitchin’, right?  Does that help?”


The eight year old nods because he already knew that.

*Sigh* “OK, beryls are a silicates that have the basic chemical composition of Be3Al2(SiO3)6, meaning the crystalline molecule forms an asymmetrical spur on one side of the molecule leading to a hexagonal crystal when the molecules are stacked, like parallelograms.  While chrysoberyls are tinier than beryls and only have one beryllium atom to form around, so their crystal structure is much more symmetrical and forms an orthorhombic arrangements, sort of like cubes with dips in the middle.  Does that help?”


Eight year old roles his eyes because everyone should know that by now.

Considering that none of you have learned anything from the prolonged inside joke above, I digress…  To find Chrysoberyls one essentially needs to find pegmatites with beryllium and that also look like they had a lot of water in them when they formed.  To find Alexandrites you find those same pegmatites but also look for evidence of there being chromium too.

The great things about gemstones is that there is always a new discovery to be found somewhere.  Once the Ural source for these groovy stones played out, other deposits began to be discovered.  Also, these pegmatites don’t just form chrysoberyls, they will have also have formed fantastic crystals of quartz, garnets, tourmaline, spinel, and corundum to boot.  So, where there are chrysoberyls there are a shit load of other stuff to make some overlord really rich.

Most significant mineral discoveries come from alluvial deposits along some river or stream.  In early 20th century discoveries of Alexandrite were made in Sri Lanka and India where the stones were nothing more than weathered pebbles found in streams.  The stones are not of the most vivid color; with color changes going from brownish-orange to yellowish-brown.  Other discoveries of Alexandrites have been made in Tanzania, Myanmar, Zimbabwe, and Brazil with most of the today’s production coming from mines in India and Brazil.

In Brazil, Alexandrites and other forms of chrysoberyls are found in the states of Espento Santos, Bahia, and Minas Gerais.  Minas Gerais means “general mines” and was settled by prospectors looking for gold.  Later, discoveries of diamonds, rhodonite, tourmalines, garnets, and everything else one would expect made it one of the great gem centers of the world.  Miners in Minas Gerais work at the earth in the most primitive fashion imaginable.  Modern mining technology isn’t really needed in an area where one can unearth a million dollar stone while digging a latrine, or putting a fence post in the ground!  Noosphere Geologic has a near flawless 8.53 carat oval cut Brazilian Alexandrite as the flagship stone in our collection.

An 8.53ct oval cut Brazilian Alexandrite that is part of the Noosphere Geologic Collection
An 8.53ct oval cut Brazilian Alexandrite that is part of the Noosphere Geologic Collection

There have been several places in North America where one can find chrysoberyls: Pend Orielle County, Washington (also home to some GIGANTIC green beryls); the Black Hills of South Dakota; the border region of Nevada and Arizona in Northwestern Arizona; in North Central Colorado in the Front Range; and all along the Appalachian Mountains (basically the same age and type of mountains as the Urals) from North Carolina, Virginia, and all throughout New England.  The only place so far, that I know of, where Alexandrites have been found in the United States is at the La Madera Mountain mine in Rio Arriba County, in central New Mexico, which is reported to produce occasional small chrysoberyl crystals with weak color change.  I have yet to see any of these stones first hand, but I plan on getting me some!

Natural Alexandrites are among the most valuable stones in the world. True, clean red/green stones sell for more than $10,000 per carat.  When the stones have more of a brownish or orange tint to the colors they sell for about $2,000 per carat; with raspberry/blue stones (common to the Brazilian variety) selling for about$8,000-$10,000 per carat.  If the stone is Russian then expect to pay $50,000 per carat.  If the stone is Russian, with red/green color change, is over ten carats, and is inclusion-free, just put a million dollar minimum on it from the get-go.

You can find a bunch of beautiful examples of lab-created synthetic Alexandrites out there, as well as imitation stones that are usually lab-created colorchange spinel or colorchange sapphire that are made with vanadium.  Sometimes you can find “crown” or “doublet” Alexandrites that have thin, real sheets of Alexandrite glued to a different stone and sold as the real thing.  If you are going to purchase an Alexandrite, take it to someone who knows what they are doing.  Look for bubbles or curved striations inside of the stone with a microscope; this is a sign that it is lab-created and should only sell for a few dollars per carat.  Also, having a certification from a reputable gemological laboratory is a good idea (like the GIA, EGL, AGL, Swiss Lab, IGTL, etc…), this will give you confidence that what you are purchasing is the real deal.  You don’t want to drop $40,000 on that engagement ring to find out that you just bought a $5 stone that was made at a lab in an office park in Bangkok!