Scientists solve a century-old mystery of yellow desert glass prized by Egyptian pharaohs

A type of exotic and magnificent glass found in the Sahara Desert has a cosmic origin, according to a new study. After analyzing the chemical composition of the Libyan desert glass – a natural glass whose bright yellow color made it a popular decorative material – the researchers discovered that it had been produced by ancient meteorite impacts.

Cosmic glass worthy of kings

Breastplate found in the tomb of King Tutankhamun. The beetle is made from glass from the Libyan desert. Credit: Wikimedia Commons.

The rare glass of the Libyan desert is prized for its beauty for thousands of years. Glass – the purest natural silica glass ever found on Earth – is usually yellow in color and can be very bright, although most parts are milky and may even contain tiny bubbles, white streaks, and black swirls d & # 39; ink.

According to one estimate, more than a thousand tons of glass from the Libyan desert are scattered in the deserts of eastern Libya and western Egypt. Most have the size of pebbles, although some pieces may be of considerable size and weight – the largest piece ever found weighs about 26 kg.

The inhabitants of the Neolithic period made glass tools, which the Egyptians later used to make jewelry. In fact, the carved stone on the breastplate of the famous Egyptian pharaoh Tutankhamun was glass of the Libyan desert. But these pieces of glass were created long before the birth of King Tut – about 29 million years ago, according to one estimate.

Silica glass to the great sea of ​​sand. Credit: Mohamed El-Hebeishy.

For over a hundred years, scientists have been debating the forces that could have created these enchanting glasses. Two major hypotheses explain their formation: either a meteorological impact or an aerial explosion (an atmospheric explosion occurring when meteorites explode in the lower atmosphere) was the cause. A recently published study supports the previous theory.

In a new study, Aaron Cavosie of Curtin University in Australia and his colleagues performed chemical analyzes of glass samples from the Libyan desert that unequivocally support the theory of meteorite formation.

While they were examining the zircon minerals contained in the glasses, the researchers found traces of another mineral called reidite. This mineral is formed only under high pressure and heat – so far it has not been found anywhere but in meteorite impact craters.

"Meteorite impacts and aerial explosions can cause melting, but only meteorite impacts create shock waves that form minerals under high pressure," says Cavosie.

"So, finding evidence of former truth confirms that it was created as a result of a meteorite impact."

Whatever meteorite hit the desert millions of years ago, it had to cause a huge explosion. It vitrifies a large area, giving a wide range of lenses from cloudy black to extremely bright lemon yellow – all depending on the type of contaminants dissolved in the liquid silica created by the powerful impact.

A variety of glasses from the Libyan desert. Credit: Corning Eyeglass Museum.

The results published in the journal Geology are useful in determining the frequency with which objects near the Earth come into contact with the surface of our planet. The study seems to suggest that impacts powerful enough to create Libyan glass in the desert are fortunately quite rare.

"Meteorite impacts are catastrophic events, but they are not common," says Cavosie.

"Air explosions occur more frequently, but we now know that we should not expect a glass formation event in the Libyan desert in the near future, which is comforting."