According to a note that came with this item: “This is one of two 'Grains' that composed a KBr cylindric boule 5" long and 5" in diameter that John Strong (1905-1992) grew in 1929, when he was a graduate student under Professor Harrison Randall at the University of Michigan. The KBr prism of the first recording infrared spectrometer was made from a subsequent successful boule. This single crystal, grown under reducing conditions, is notable in being free of cloudiness throughout. John Strong." John Donovan Strong (1905-1992) was a noted American astronomer and optical scientist.
