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Chemistry In Pictures

Chemistry in Pictures: The oldest thing on Earth

by Brianna Barbu
November 22, 2023

A dark gray rock with white inclusions, sitting on a table in front of a dark background.
Credit: Chip Clark/Smithsonian Institution National Museum of Natural History

The people at the Smithsonian Institution National Museum of Natural History were nice enough to give a couple members of the Chemistry in Pictures team a behind-the-scenes look at their mineral collection. For the next couple weeks, we’ll bring you photos of some of the minerals that wowed us, some of which are billions of years old.

A man standing in a geology lab holding a chunk of meteorite. His head is turned downward to look at the specimen. while two other people in the background look on.
Credit: Brianna Barbu/C&EN
Chempics editor Manny Morone admiring a piece of the Allende meteorite

The oldest minerals on Earth actually came from space. This is a piece of the Allende meteorite, and those light-colored bits (called calcium-aluminum-rich inclusions, or CAIs) date back to the formation of our solar system, 4.65 billion years ago. If you chopped the meteorite up in a blender and analyzed it, you would find it has the same elemental composition as the Sun and Earth and everything else that formed from the nebular components that our solar system came from, says Elizabeth Cottrell, chair of the department of mineral sciences at the National Museum of Natural History. “It contains all of the elements that make up everything we are.”

The Allende meteorite, which arrived on our planet on February 8, 1969 near the village of Pueblito de Allende in Mexico, was about the size of a car before it hit our atmosphere and exploded into thousands of smaller pieces. It’s one of the most studied meteorites in the world and an integral source of information about the chemistry of our solar system, including clues about the origin of Earth’s water.

A close-up of a dark gray meteorite with white inclusions.
Credit: Chip Clark/Smithsonian Institution National Museum of Natural History

Credit: Chip Clark/Smithsonian Institution National Museum of Natural History (table specimen, close-up); Brianna Barbu/C&EN (person holding rock)

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