A meteorite crashed into the sands of Egypt and Libya 28.5 million years ago, creating a luminous yellow glass called Libyan desert glass. One piece found its way into the tomb of ancient Egypt’s King Tutankhamen.
It’s the mid-Oligocene epoch. The world’s first cats have just come into being, and much of Europe is underwater. If you were a creature walking in the sands south of Egypt’s tropical forests, you might have looked up into the sky to see a bright light coming towards you, fast.
When this meteorite smashed into the earth, its immense heat and pressure turned the landscape into a scorching oven, instantly liquifying the silica sands. When the shock waves subsided and the smoldering landscape cooled, the molten sand solidified into countless little chunks of clean, vibrant yellow-green glass, left strewn across a vast stretch of harsh land.
In the next 28.5 million years, the Arabian Peninsula split from Africa and formed the Red Sea. Ice ages came and went, mind-boggling arrays of species evolved and went extinct, and human beings were born.
Proportionately, if one day has passed since the meteor impact, modern humans have been around for only 15 minutes. During that quarter-hour, the Sahara has oscillated back and forth between wet and dry every minute. About 15 seconds ago, colossal stone pyramids started to sprout along a riverbank, near the Egyptian desert. The last time you took a breath, two nations decided to draw a straight line through the sands.
Desert Glass in the Afterlife
All the while, the desert glass sat unhurried in the shifting sands. One day, likely in the 2nd century B.C., someone meandering through the dunes spotted a glint of light and bent down to pick up a particularly luminous piece of glass, the color of sun shining through a yellow-green leaf. It was small enough to fit in the palm of their hand, but precious enough to be carried some 450 miles to the lush shores of the Nile River, where an ancient Egyptian civilization was flourishing.
There, a teenage king named Tutankhamun ruled, but not for long. Though his 18 years of life were a single heartbeat in the life of the Earth, he earned a high profile in human history. The discovery of his treasure-filled tomb in 1922 made King Tut Egypt’s most famous pharaoh. The crown jewel of his riches is now one of humanity’s most renowned artworks—a gold death mask, striped with turquoise, lapis lazuli, and other stones.
But amongst the precious clatter of history, archaeologists also found the pharaoh’s breastplate, intricately crafted from gold, silver, and precious jewels. At the center sits a symbol of the sun god Ra—a winged scarab beetle inlaid with a jelly-like yellow glass that seems to glow from the inside.
This scarab is the only known ancient Egyptian artwork to use desert glass. At the time, humans had only just figured out how to make glass (mimic a meteor strike by superheating then cooling sand). This chunk of translucence was as precious as a gemstone.
Today, the breastplate sits in the Egyptian Museum in Cairo, but will be moved to the much grander Grand Egyptian Museum in Giza when it opens next year.
Libyan Desert Glass
This meteorite-made material is now known as Libyan Desert Glass (LDG). Somewhat unceremoniously, it is now widely available for purchase on Ebay.
Still, it can only be found scattered around a Delaware-size area in the remote heart of the Great Sand Sea, an expanse of dunes three times bigger than Montana that straddles the border between Libya and Egypt. On both sides, the closest roads are hundreds of miles away.
Collecting the glass today is an arduous undertaking, complicated by Libya’s political chaos (the nearest Libyan town, Kufrah, is held by renegade military commander Khalifa Haftar). According to one geologist, the Egyptian government was requiring military escorts to the region in 2016 and not allowing LDG to be taken out of the country.
But this region was not always desert—Paleolithic blades and sickles made of stone and desert glass have been found in the sands, suggesting the region could once have hosted farmed grasslands and lakes.
The fickleness of the landscape has long made the origin of LDG a mystery. Natural glass occurs when molten rock rapidly cools, and melting rock requires the extreme heat of either a volcano or an incoming meteorite. But there is no volcano in the area and silica glass as pure as LDG needs extraterrestrial temperatures to form.
This would suggest a meteorite, but no impact crater has ever been found in the Great Sand Sea. To complicate things, geologists speculate that the ground was higher when the glass formed—possibly up to 1,000 feet, according to geologist Norm Lehrman—so an ancient impact crater could have eroded away over time.
Geologists suggested in 2013 that a meteorite exploded in the air above the desert, in an event called an airburst. Akin to an atomic bomb, such an explosion could have generated upwards of 3,600o Fahrenheit—enough to melt the sand below without leaving a crater. This theory has gotten a lot of play.
A Smoking Gun
According to their new research, geologists Aaron Cavosie and Christian Koeberl say they have unequivocally proven that a meteorite impact, not an airburst, made the cosmic glass.
Their “smoking gun” is found in traces of a rare mineral called reidite, which only forms when meteors actually hit the earth. Under the incredible pressure of a meteor strike, a common mineral called zircon is squished into a more compact arrangement—reidite.
But if the rocks then melt, which most do in the heat of the impact, the new mineral reverts to zircon, making lasting reidite very rare. However, the structure of leftover zircon always bears the memory of being reidite, as a crumpled piece of paper will have creases even if uncrumpled. Geologists have worked out some befuddling geometry to read the past of those molecules.
The Libyan desert glass no longer contains any reidite. But in its microscopic grains of zircon, Cavosie and Koeberl found whispers of the molecule, which existed for a blink of an eye, 29 million years ago. This simple fact makes them confident that Libyan desert glass only could have been formed in the crush of plummeting space rock. Estimating the meteorite’s size is near impossible without physical remnants of it, but its crater was likely “much larger than one kilometer in diameter,” Cavosie told Inside Arabia.
Impact of an Impact
Meteorites have created other kinds of glass, but LDG is regarded as something special. Geologists describe the glass like a poet might a beloved, with words like “silky chatoyance,” or the more technical “braided matrix of viscously flow-banded ribbons.”
The glass took on many shapes, colors, and clarities, but the cloudy yellow-green gems, polished by millions of years of wind-driven sands, draw most admirers—like King Tut’s jewelers. It’s one of the purest natural glasses, simply silica atoms jiggled into an alluring, even sacred, configuration by a fiery, earth-shaking cataclysm; a gem fit for a Pharaoh.