The path to Betterndorf's achievement began when samarskite specimens containing gadolinium were collected in North Carolina and then analyzed in Massachusetts. In 1875, the Boston Natural History Society published Ellen H. Swallow's analysis of samarskite nuggets discovered in loose soil in North Carolina the previous year. Miss Swallow, who was born in Massachusetts and worked in Boston, found iron (14 percent), uranium (10 percent) and yttria (13 percent) with lesser amounts of cerium, tin and manganese. "Yttria" is a plural form, used to indicate that the element yttrium and another similar substance occurred together. The other substance was later found to be gadolinium. Miss Swallow's analysis confirmed the identity of the nuggets as consistent with samarskite found in 1852 in Rutherford County, North Carolina, as well as specimens collected in 1809 near Miask, Russia, in the Urals. She decomposed the specimens by hand in her lab with sulphuric acid to separate the components before precipitating the elements, including the uranium. Later, Ellen Harriet Swallow Richards (her married name) founded the science of home economics.
In the August 1886 issue of the Journal of the Chemical Society, a single sentence notice announced that Swiss chemist Jean Charles Galissard de Marignac, working in Geneva, had decided that the element he had previously identified as yttria alpha (Yα) should henceforth be called gadolinium. In 1880, while studying yttria in samarskite, Marignac had found two absorption spectra for yttria. He decided that Yα was the oxide of a new element. Marignac had been working with Mitchell County, North Carolina, samarskite collected in 1874, which Miss Swallow had confirmed.
In 1885, French chemist Paul Emile Lecoq de Boisbaudran, who worked in Paris, confirmed Marignac's work by duplicating his isolation of the Yα oxide and measuring the spectrum absorption as the same. With Marignac's consent, Lecoq de Boisbaudran named the new element gadolinium after Finnish chemist Johann Gadolin, who did the first work with yttria. The name was controversial: Naming elements after fellow scientists was inappropriate, plus an yttrium-bearing mineral gadolinite had already been named for Gadolin.
The element gadolinium is not the same as the mineral gadolinite. In the 1780s, chemist Carl Arrhenius was stationed with an artillery regiment on the island of Roslaga, near Stockholm. In a quarry at the village of Ytterby, he collected a generally flesh-red feldspar associated with a granitic gneiss. His collection reached Johann Gadolin at the University of Abo, Sweden, now Turku University in Finland. Gadolin investigated a mineral in the feldspar that was heavy and black and had no fracture plane. Arrhenius had named the black mineral ytterbite, but it was later called gadolinite. The element yttrium was isolated from gadolinite.
There are 39 isotopes of gadolinium (Gd, atomic number 64). Seven isotopes are stable, and two radioactive isotopes have a half-life so long that they still persist in Earth's crust and can therefore be regarded as stable. Gadolinium can be used as control rods in nuclear reactions, as contrast agents in magnetic resonance imaging, in microwave technology, and for color in television.