How the Mineral Zircon Became Earth's Best Timekeeper : Short Wave The mineral zircon is the oldest known piece of Earth existing on the surface today. The oldest bits date back as far as 4.37 billion years — not too far from the age of Earth itself at about 4.5 billion years old. And, unlike other minerals, zircon is hard to get rid of. This resilience enables scientists to use zircon to determine when major geological events on Earth happened. As part of our series on time, host Aaron Scott talks to science correspondent Nell Greenfieldboyce about why this mineral is often considered a geologic clock and has earned the nickname "Time Lord."

This episode is part of our series, "Finding Time — a journey through the fourth dimension to learn what makes us tick." Read more of Nell's reporting on zircon here.

Curious about other aspects of our universe? Email us at ShortWave@NPR.org.

Zircon: The Keeper Of Earth's Time

Zircon: The Keeper Of Earth's Time

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Stanford University/Getty Images
This enlarged image shows a .05-millimeter-long zircon.
Stanford University/Getty Images

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The mineral zircon is the oldest known piece of Earth existing on the surface today. The oldest bits date back as far as 4.37 billion years — not too far from the age of Earth itself at about 4.5 billion years old. And, unlike other minerals, zircon is hard to get rid of.

"Things like quartz, things like feldspar — they are chemically and physically eroded until they are no longer quartz and feldspar," says Michael Ackerson, a geologist at the Smithsonian's National Museum of Natural History. "One of the main reasons that zircon is so useful is that zircon is very resilient."

This resilience enables scientists to use zircon to determine when major geological events on Earth happened. As part of our series on time, host Aaron Scott talks to science correspondent Nell Greenfieldboyce about why this mineral is often considered a geologic clock and has earned the nickname "Time Lord."

This episode is part of a series called "Finding Time — a journey through the fourth dimension to learn what makes us tick." Read more of Nell's reporting on zircon here.

Curious about other aspects of our universe? Email us at ShortWave@NPR.org.

Listen to Short Wave on Spotify, Apple Podcasts and Google Podcasts.

This episode was produced by Thomas Lu, and edited by Gisele Grayson and Rebecca Ramirez. Abe Levine checked the facts. Our audio engineer was Gilly Moon. Brendan Crump is our podcast coordinator, Beth Donovan is our senior director of Programming and Anya Grundman is our senior vice president of Programming.