Discovery
Around 1920, Justo Daza, an accomplished mine worker, and Fritz Klein, a mining engineer, were scrambling over Chivor's steep mountain-side terraces–a legendary emerald site in northeast Colombia. Long iron poles and explosives inserted into drill holes were tearing rocks apart. They looked for new emerald veins and found none.
Let's continue ahead, said Klein. This is a dead place.
No, no, no, urged Daza. I believe that, there is an emerald here.
Klein shrugged: Well, one shot more-but that's it.
We upped the explosive dosage and blew a gaping hole open, exposing enticing glints of a mineral vein. Klein flung his arm into the hole and started to rumble along. He fished out quartz pieces, feldspar and apatite-a mineral containing phosphate similar to that present in bones and teeth.
He sampled deeper, until he finally closed his hand around something tall, facial and exciting. Klein knew without even trying, that he must have hit gold.
The prospectors had found what would come to be called the Patricia Emerald: a sparkling 12-sided diamond about the size of a soup bowl, weighing 632 carats–more than a quarter of a pound–with a green hue so bright and vibrant that you would swear the stone was photosynthesizing.
Klein sold the discovery for tens of thousands of dollars when Daza "was given $10 and a mule, unsurprisingly enough," said Terri Ottaway, museum curator at the Gemological Institute of America.
Yet the public has still got the best deal of all. Later, the stone was donated to the New York American Museum of Natural History. Today, the Patricia remains one of the world's largest uncut emeralds, and will be a featured star when the museum's gem and mineral halls renovation is completed in 2019.
The Patricia encapsulates a often overlooked characteristic of gemstones in its raw, columnar elegance, particularly those that we find "precious"-diamonds, rubies, sapphires and emeralds.
We may covet the stones for sparkling personal ornamentation and status; we may imbue them with passion, exoticism and the Hollywood diamond heist titillation. But their true strength resides in the dynamo they disclose that created them: Planet Earth.
A gemstone is a sign in a glass, for scientists. Except for the note, the bottle is a gleaming hint to the intense human, chemical, and tectonic powers at deep underground work.
In fact, all of the characteristics that helped catapult the Big Four into fame in the first place–their extraordinary hardness, the complexity and beauty of their shading, their rareness–are also essential to the technical interest of the jewels.
Precious gems are born of strife: of marriages of weapons between violent chemical species, and they are hard enough to withstand cataclysms that kill everything about them.
"Earth is an awesome, massive chemical laboratory and it's a filthy place to produce crystals," said Jeffrey Post, curator of the National Gem and Mineral Collection at Smithsonian. But these impurities provide gems with their color and character, and "give us crucial knowledge about the crystal structures."
Gem science rules aren't carved into place. Researchers have recently been surprised to find that some of the world's finest and most expensive diamonds, which can sell for hundreds of millions of dollars, emerged 250 miles or more below the surface— twice the depths historically recorded for diamond nurseries on Earth.
Some diamonds turn out to be remarkably youthful: two-billion to three-billion years old rather than the normal gem. Other researchers associated the production of ruby with collisions between continental land masses and proposed that the red jewels be named "plate tectonic gems."
A team at the University of British Columbia studied newly discovered sapphire deposits in the Nunavut territory of Canada and concluded that the stones were formed by a new three-part geochemical "recipe" unlike any mentioned elsewhere in the world for sapphire formation.
You continue with calcareous sediments that contain just the right mineral impurities –nepheline is a must–and you squeeze and heat the rocky weight to 800C. You add fluid to it and you cause it to cool. Finally, only as there are signs of disturbance in the increasing mineral assemblage, you inject another fluid shot and lock the crystal into place. Complete time to cook: about 1.75 billion years.
"If one step is left out," said the geologist at the University of British Columbia, Philippe Belley, "you don't get the sapphires."
Geologists in the past have sometimes regarded gemstones as baubles and the study of gems as oxymoronic. "Gems were deemed crass industrial products and beyond an academic's honor," said George Harlow, Earth and Planetary Science curator at the American Museum of Natural History.
The refracted light was most commonly used by geologists. "My colleagues know a gem course as an important part of an undergraduate degree is a really strong attraction," Harlow said.
"If you can demonstrate how gems are made, or the properties they have, it takes a lot of chemistry and physics to understand that." "That's a perfect way of bringing customers through the house," he said. "When you put up a geology-speaking tag, no one comes. Yet if you're thinking,' This way to Diamond Hope,' then everybody needs to hear more.
Harlow suggested that precious gems acquired a part of their prestige by associating them with gold. The gems ended up clustered as insoluble stones at the bottom of stream banks, mostly in the presence of equally insoluble rock.
Long coveted for its ductility, elegance and oxidation resistant, gold was considered the wealth of rulers and kings–so why didn't the gleaming stones find next to it?
The word diamond derives from the Greek words "indestructible" and "that which can not be tamed," Harlow said, "and those related metaphysical properties made the ruler appear even more impressive."
Diamonds are not indestructible, but they are the hardest known objects, despite the Mohs hardness scale peak score of 10–that is, scratch resistance.
Hind the untameability of a diamond is its three-dimensional structure, a repeated crystalline lattice of carbon atoms, each of which is closely connected to four neighbors above, below and on either side. By comparison, in graphite, carbon atoms are only bonded together in two-dimensional sheets, and would flake off with the mere act of placing pencil to paper.
To force vast quantities of carbon atoms to bind their limbs in both directions includes Stygian high-heat and friction whips, which could only be located underwater until recently.
Diamonds must be immediately fired from below-say, from a volcanic explosion-or they will end up in your stocking as much gas. Researchers also found diamonds that had blundered slowly enough crustward to extend their carbon bonds, leaving a stone with a diamond shape with graphite consistency.
The reversion method in the laboratory was recapitulated by Gareth R Davies, a geology professor at Vrije Universiteit Amsterdam, and his colleagues. "Yeah, we're getting diamonds, and transforming them into work graphite," he said. "So my mom asks why I am so crazy."
Researchers may also produce diamonds in the laboratory, but the findings are destined to industry more frequently than Tiffany. Nor can physicists build something even as celestial as the Hope Diamond: the largest deep-blue diamond in the world, with a similar back-story.
The diamond was discovered in England, sold in 1668 to King Louis XIV of France and looted after the French Revolution. This reappeared 50 years later when the Dutch businessman Henry Philip Hope's stock–hence its name–was sold by Hope's bankrupt successor and then transferred from hand to occasionally poor hand, picking up an odor on the way to "cursing."
When Jeweller Harry Winston donated the diamond to the Smithsonian Institution in 1958, sending the huge gem blithely through the mail from New York to Washington, the fame of the diamond burst. As the then-first Lady Jackie Kennedy negotiated a one-month diamond loan to the Louvre in Paris, the National Gallery of Art in Washington received Mona Lisa from Da Vinci in exchange.
Scientists have since put the 45-carat diamond in their arsenal for a non-invasive device, trying to explain the exact distribution of boron atoms that offer the Hope its steely blue color and why the diamond glows, or phosphoresce, a translucent hue of orange blood when exposed to ultraviolet light.
Post assumes the phosphorescence is the result of reactions between impurities of boron and nitrogen in the near-flawless carbon structure of the diamond.
In the evolution of colored gemstones, coloration mechanisms still feature more prominently. After all, sapphires and rubies are made from the same simple mineral, corundum, a crystallized aluminum and oxygen combination that would be translucent and colorless if not for any meticulous chemical doping.
Corundum is a red ruby by timely incorporation of chromium atoms with a Mohs hardness level just a point short of diamond's. New work shows that as continental land masses rub together, chromium is pushed back to the surface from Earth's mantle.
A sapphire is a corundum crystal of any color except red–but a genuine sapphire is known by many to be blue. In this case, the blue comes from electrons jumping back and forth scattered in the crystal from near-homeopathic concentrations of iron and titanium atoms.
"It's called conversion of the fee for intervalence," Harlow said. "You can't even quantify the sum of iron and titanium but a drastic color is created by the tiny impact."
Emerald is the softest of the precious metals, with a Mohs value between 7 and 8, and is a bit of fossilized marsh at its best. The mineral base, beryl, is primarily aluminum and silicone, with a vital beryllium infusion: a thin, rare and highly toxic element.
"If you're talking of making your own emeralds, then don't," Ottaway said. During mountain growth, emeralds form when shale and calcareous rocks are raised and compressed.
"It is a big squeegee effect, pushing hot solutions around," explained Ottaway. Salt dissolves in the hot sludge, making it into brine, and the brine is trapped in pockets which then serve as wetlands, collecting organic matter and toxic metals, including beryllium, which is then absorbed into rising aluminum silicate crystals.
The coloring agents are trace amounts of vanadium and chromium which can make a ruby red but replicate green in the sense of the beryl structure.
The green for emeralds born in Colombia's mountains is chromatic, spectacularly white. Pyrite deposits suck up all iron in the region which will otherwise adulterate the refractive properties of crystal and muddy beryl.
"That is why emerald Colombians are so awesome," said Ottaway. "One of these beautiful stones you can get so lost looking at."
Forget the mule or gold, or three wise myrrh-like guys: this piece of evergreen is pure holiday cheer.