Years ago, an Egyptian geologist had found a black pebble in the Libyan Desert Glass, yellow silica glass that covers 2,316 square miles of the Sahara Desert. In a study that will be published in Earth and Planetary Science Letters in November concluded that the black pebble had come from a comet that struck Earth over Egypt 28 million years ago, marking the first evidence of such an occurrence happening.

“It’s a typical scientific euphoria when you eliminate all other options and come to the realization of what it must be,” lead author Jan Kramers, a geology professor at the University of Johannesburg, said in a statement. The team of researchers conducted chemical analyses, which included Raman spectroscopy, X-ray diffraction and transmission electron microscopy to prove that the pebble did come from a comet, not a meteorite.

Called, Hypatia, the comet pebble is described as “angular, black, shiny, extremely hard and intensely fractured,” and contains diamonds, a result of the comet’s shock as it hit Earth. The carbon makeup shown by the appearance of diamonds is what helped the scientists confirm the pebble was not from a meteorite. “If you compare it with meteorites … they contain only about three percent carbon. And this thing contains 65 percent carbon,” Kramers.

The comet exploded as it entered Earth’s atmosphere, heating up the sand to 3,632 degrees Fahrenheit. What remained of the comet became the Libyan Desert Glass, a piece of which remains in King Tutankhamun’s brooch.

“Comets contain the very secrets to unlocking the formation of our solar system and this discovery gives us an unprecedented opportunity to study comet material first hand,” David Block, an astronomy professor at Wits University, in Johannesburg, said in a statement.

Comet fragments have historically been very difficult to find for scientists. With the exception of dust particles and some carbon-rich dust in the Antarctic ice, scientists have had very little luck finding any comet material. “Comets always visit our skies — they’re these dirty snowballs of ice mixed with dust—but never before in history has material from a comet ever been found on Earth,” Block said.

Scientists are hoping that challenge will have become easier with the techniques used to identify Hypatia. “NASA and ESA [European Space Agency] spend billions of dollars collecting a few micrograms of comet material and bringing it back to Earth, and now we’ve got a radical new approach of studying this material, without spending billions of dollars collecting it,” Kramers said.