Zircon is a mineral that’s commonly used as a gemstone in jewelry. It’s notable for its high refractive index and strong dispersion, which give it a brilliance and fire that can rival that of diamond. However, unlike diamond, zircon is not a single element but a zirconium silicate that can contain traces of uranium and thorium. These radioactive elements make zircon an important tool for geologists, who can use the rate of their decay to accurately date geological events that occurred billions of years ago. In fact, the oldest material ever discovered on Earth is a tiny zircon crystal from Western Australia that’s estimated to be over 4.4 billion years old! This makes zircon literally as old as the Earth itself.
