Astatine: An Element That Vanishes Almost Immediately

Astatine is among the rarest naturally occurring elements in Earth's crust. It is produced in decay chains of heavier elements, but its isotopes decay quickly. A widely repeated estimate puts the total amount in the entire crust at less than 30 grams at any moment. This is a model-based estimate: scientific sources also report much lower figures, depending on assumptions and what is being counted.