4.4-billion-year-old time crystals

You may have seen, years ago, commercials for cubic zirconia—a synthetic diamond substitute —and been unimpressed.But naturally occurring zircon crystals, made from zirconium silicate, are another story.Zircon crystals are extremely durable, resistant to melting, cracking, dissolving, or crushing, and able to withstand repeated cycles of metamorphism and erosion.This makes them the longest lasting—and oldest—minerals on Earth.If that’s not impressive enough, they also have a natural clock within them.Uranium atoms have the same charge as zirconium atoms so they’re able to sneak into zircon crystals in trace amounts.The uranium decays radioactively into lead over time, and the ratio of uranium to lead in a zircon crystal can precisely tell its age.Recently scientists found tiny zircon crystals from western Australia that were 4.38 billion years old.Bear in mind that Earth itself is about 4.5 billion years old, so these crystals hold important clues to its beginning.Analysis of oxygen isotopes within the crystals revealed they formed in a water-rich magma. Traces of titanium point to cooling at temperatures found in plate boundary subduction zones.These findings suggest that Earth had more water—and active plate tectonics—hundreds of millions of years earlier than currently thought.All that from a tiny, but very impressive, crystal.