Astatine is a very rare radioactive chemical element with the chemical symbol At and atomic number 85. It occurs on Earth as the decay product of various heavier elements. All its isotopes are short-lived; the most stable is astatine-210, with a half-life of 8.1 hours.
This is only an illustration, not astatine itself. Crystals similar to iodine, but darker in color than these, which due to the extreme radioactivity glow blue and evaporate to dark purple gas - Chemical ELements A Virtual Museum, CC BY 3.0 <https://creativecommons.org/licenses/by/3.0> source: https://images-of-elements.com/astatine.php