4.4 billion years ago, the Earth was in what is called the ‘Hadean Eon’. This time period is poorly understood, because there is no rock record dating from that time. This is where the zircon mineral grains come in. ... In a sense, these zircon grains are the missing pages. Zircon’s chemical name is zirconium silicate, and it’s found almost everywhere in the Earth’s crust. This study focuses on what’s called detrital zircon, which is formed in igneous rocks, but then survives over time until deposited in sedimentary rocks. Zircon grains are typically very small, about 0.1 to 0.3 mm...