boards that chose the textbooks for their schools. Research on rare earth elements In 1787 Carl Axel Arrhenius found a dark mineral in a feldspar mine in the village of Ytterby, Sweden. He sent a sample of this ytterbite to Johan Gadolin for further analysis. A number of researchers tried to identify elements composing the ore, which were particularly hard to separate due to their similar chemical properties. As a group, they were given the misnomer rare-earth elements. (In fact, they are not rare, just difficult to extract.) Individually, they were discovered and named by various scientists, often using variants based on the word "Ytterby". The first two ores to be derived were called ceria and yttria. In the 1830s and 40s, Carl Gustav Mosander derived several substances from these known ores. In 1843 Mosander was able to extract three metal oxides from ytteria, a whitish "earth" which he called pure ytteria, a pink or rose-colored oxide which he called terbia, and a yellowish peroxide which he called erbia. Mosander was rightfully uncertain of their purity; they did however contain the elements yttrium, erbium, and terbium. Like scientists before him such as Mosander and Arrhenius, Berlin also worked on separation of ytteria ore into its constituent compounds. In 1860, Berlin successfully reported the identification of two substances, yttrium, and a pink salt which Berlin named erbium. Subsequent chemists followed Berlin's designation rather than Mosander's. The naming of ytteria's components became further complicated in 1862, when Marc Delafontaine reported its separation into yttrium and a yellow peroxide, which he first called mosandrum (after Mosander) and later terbium. In this way, the names originally given to erbium and terbium became switched. References External links Nils Johan Berlin Nils Johan Berlin 1812 births 1891 deaths Swedish chemists Academic staff of Lund University Members of the Royal Swedish Academy of Sciences Rare earth scientists