This Is The Rarest Substance On Earth

Humans place a premium on uncommon objects because of a cognitive shortcut called the scarcity heuristic. Psychology Today explains that the "scarcity heuristic states: If something is rare, it must be valuable." It's the reason why a wealthy shoe enthusiast coughed up $437,500 to own an extra-rare pair of Nike Moon Shoes, why "a one-of-a-kind penny" that was accidentally cast in bronze was bought for $1.7 million, and why diamonds are a girl's best friend while coal gets the cold shoulder. 

If someone was willing to shell out 170 million regular pennies for one rare penny, perhaps the world's biggest spenders would pay their prettiest pennies for the rarest substance on Earth. What's the rarest substance? Glad you (probably) asked. 

Earth's rarest substance plays extremely-hard-to-get

Astatine sounds like an artificial sweetener, but it's actually the ultimate whack-a-mole of elements. Dmitri Mendeleyev, who created the periodic table of elements and became the bane of every chemistry student forced to learn those elements, first predicted the existence astatine in the 1800s, according to Live Science. But the substance is so uncommon that it took 70 years to discover. In fact, at any given moment only 25 grams of the stuff naturally occurs on Earth.

The name 'astatine' comes from the Greek word for "unstable" (astatos) and it lives up to its name. It doesn't live long, though. The astatine isotope with the longest half-life, astatine-210, only boasts a half-life of about 8 hours. Luckily, it doesn't stick around very long because it's "highly radioactive," and that short-half life prevents it from posing a health or environmental threat. 

Earth's rarest substance also plays extremely-hard-to-study

Because samples of astatine are here today and gone ... probably also today, it's extremely tough to suss out the ins and outs of the element. Scientists know that it's the heaviest known halogen element and that it melts at 576 degrees Fahrenheit (302 degrees Celsius). They think it has a dark color but are in the dark about what its actual color is. Some researchers believe astatine might have iodine-like properties and because of its radioactivity, scientists are eyeing it as a potential cancer treatment. How much would astatine sell for at an auction? Who knows? But if it could heal a cancer patient, it's priceless.