How Old Is My Zircon?

Is Zircon the Oldest Mineral?

Zircon is the oldest known mineral on Earth. The oldest surviving zircon crystals are approximately 4.404 billion years old. This means zircons were present on Earth even before life began. To put this in perspective, consider this: humans are much closer in time to dinosaurs than dinosaurs are to the oldest zircons.

The oldest zircon crystal samples were discovered as detrital minerals in metamorphosed sediments in the Jack Hills, Western Australia. (See Wilde et al., 2001). However, these zircons are considerably older than the rock in which they are found. The primary rock source for these crystals remains unknown.

Zircons have formed throughout the Earth’s history. They can occur in igneous and metamorphic rocks as well as sedimentary rocks like sandstones. As a result, mineralogists and petrologists can often determine the age of rocks by analyzing any zircons in them. For example, geologists have discovered rocks in the Acasta Gneiss Complex in northwestern Canada that contain native zircons. S. A. Bowring and I. S. Williams note that these tonalitic orthogneisses incorporate zircon grains that are approximately