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We don’t know what astatine looks like, because, as Lowe put it, “that stuff just doesn’t want to exist.” It’s so radioactive (with a half-life measured in hours) that any large piece of it would be quickly vaporized by its own heat. Chemists suspect that it has a black surface, but no one really knows. There’s no material safety data sheet for astatine. If there were, it would just be the word “NO” scrawled over and over in charred blood.
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Randall Munroe (What If?: Serious Scientific Answers to Absurd Hypothetical Questions)