World Records
The Rarest Elements and Materials on Earth: Astatine, Francium, and Beyond
At any given moment, the entire Earth's crust contains less than 1 gram of astatine — less than a sugar crystal. Francium, the next rarest natural element, has perhaps 30 grams present in the entire planet at once. These elements are not rare because they formed in limited quantities: they are rare because they decay so rapidly that any amount produced vanishes before it can accumulate. At the other extreme, materials like antimatter — produced only in particle accelerators — cost an estimated $62.5 trillion per gram, making them the most expensive substances ever made. Rarity in the material world has several distinct causes, and each one tells a different story about nuclear physics, geology, and thermodynamics.