Template:POTD/2012-10-08
Sublimed dendritic thulium, with an argon arc remelted 1 cm3 cube for comparison. Thulium is a bright silvery-gray rare-earth metal that was discovered by Swedish chemist Per Teodor Cleve in 1879. It is never found in nature in pure form, but it is found in small quantities in minerals with other rare earths.Photo: Alchemist-hp