Chances are, you’ve heard of obsidian. It’s known as “Dragonglass” in the Game of Thrones universe, and here in our world, the stone is also born of fire. Obsidian forms when molten rock rapidly cools after a volcanic eruption, and depending on the minerals within it, the glassy substance ranges from jet-black, to shades of brown, grey, and red. But unbeknown to most, the deserts of western Kazakhstan are speckled with obsidian of a different color: a mysterious, vibrant-blue Dragonglass that can be found there, and there alone.
It’s called tengizite, and though the rare glass’ presence has puzzled many a passerby, its origin story is no secret. The truth is, we created it by mistake.
Tengizite is a non-natural form of obsidian glass – a “pseudo obsidian” – the result of an explosion that set the Tengiz oil field on fire in 1985. During this period, Russia still controlled Kazakhstan and its natural resources, and the fire turned out to be one of the longest-burning blowouts in the history of the Russian-Soviet oil industry. The Earth melted beneath its fury.
How could an oil fire melt rock? To understand this, we need to understand what crude oil really is. Unseparated crude contains a high proportion of dissolved gasses like methane, hectane, and hydrogen sulfide. As pressure drops, those gasses are released, which (quite literally) adds fuel to the fire. Much like what you’d get by spraying an aerosol can into an open flame, an oil-well fire often looks more like blowtorch than a flaming puddle — a 100-story blowtorch.
The Tengiz wells are some of the highest-pressure wells in the world, and the 1985 fire burned at an unimaginable 3,000 degrees Fahrenheit (1684°C). For a bit of perspective, that’s 500 degrees above the melting point of steel, and 1,000 degrees hotter than the temperature of most flowing lava.
Footage from the Tengiz Well 3 Blowout, 1985. Source: Bindigos
In addition to unleashing the flames of hell, the blowout sent deadly plumes of noxious gas some 980 feet (298 meters) into the desert sky, which local fire crews lacked the expertise and equipment to contain. It took just over 12 months to cap the well, and all the while, the ground below was exposed to the fire’s extreme heat.
Run of the mill obsidian forms from molten rhyolite, a high-silica volcanic rock. If it cools fast enough, the minerals floating within the magma are “frozen,” meaning they can’t reform their crystal structure within the viscous goo. As it hardens, what we’re left with is smooth silica glass that contains only small traces of those minerals. The clearer the obsidian, the fewer microscopic crystals have formed inside of it. This piece for example, contains fragments of black magnetite, and red limonite (iron oxide):
Just like rhyolite, the sedimentary rock that surrounds the Tengiz oil well is high in silica, and just like obsidian magma, it melted, then rapidly cooled after the well was capped. This explains tengizite’s similarly vitreous (glassy) sheen and fracture pattern. But why is it blue? While some specimens of so-called “rainbow obsidian” do posses a slight blue-green tint, no volcanic glass has been found to date that rivals the intensity of the oil field anomaly’s signature hue.
Some suspect the color was caused by residues from firefighting foams used on the blowout. Others point to industrial equipment like bulldozers that melted during the ordeal, suggesting their components (paint, tinted glass, etc.) could have melded with the surrounding sand. The more likely explanation, however, is that the color comes from trace chemicals and minerals that emerged from the oil well itself, or that were pumped through the sand to aid in the extraction process.
An Eiffel 65-approved look isn’t the only thing that separates tengizite from common forms of obsidian: it’s also far less brittle than its volcanic counterpart. But that doesn’t necessarily mean it’s the better choice for a Crow in need.
A brittle substance isn’t great for a smash-and-grab job, but there’s a reason humankind has fashioned weapons and tools from obsidian for millennia. When edged properly, obsidian blades are thinner and sharper than the finest medical-grade steel scalpels. What they lack in blunt force, they make up for in finesse. Today, obsidian is used in some of the most precise surgical operations.
Before you head to eBay in search of tengizite for your own collection, though, I should warn you that very little glass has been removed from the blast site. It’s likely that much of the “tengizite” you’ll find for sale actually hails from another source. One such source is ore smelting, the process by which a desired base metal (like cast iron) is separated from its raw ore. Smelting produces “slag,” a silica-glass byproduct that is colored by compounds and impurities that were removed from the ore. Though it’s often speckled with cement-like inclusions, a quick browser search for “slag blue” shows you just how similar these glasses can look to tengizite.
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