It's Elemental

The mineral gadolinite ((Ce, La, Nd, Y)₂FeBe₂Si₂O₁₀), discovered in a quarry near the town of Ytterby, Sweden, has been the source of a great number of rare earth elements. In 1843, Carl Gustaf Mosander, a Swedish chemist, was able to separate gadolinite into three materials, which he named yttria, erbia and terbia. As might be expected considering the similarities between their names and properties, scientists soon confused erbia and terbia and, by 1877, had reversed their names. What Mosander called erbia is now called terbia and visa versa. In 1878 Jean Charles Galissard de Marignac, a Swiss chemist, discovered that erbia was itself consisted of two components. One component was named ytterbia by Marignac while the other component retained the name erbia.

Marignac believed that ytterbia was a compound of a new element, which he named ytterbium. Other chemists produced and experimented with ytterbium in an attempt to determine some of it's properties. Unfortunately, different scientists obtained different results from the same experiments. While some scientists believed that these inconsistent results were caused by poor procedures or faulty equipment, Georges Urbain, a French chemist, believed that ytterbium wasn't an element at all, but a mixture of two elements. In 1907, Urbain was able to separate ytterbium into two elements. Urbain named one of the elements neoytterbium (new ytterbium) and the other element lutecium. Chemists eventually changed the name neoytterbium back to ytterbium and changed the spelling of lutecium to lutetium. Due to his original belief of the composition of ytterbia, Marignac is credited with the discovery of ytterbium. Today, ytterbium is primarily obtained through an ion exchange process from monazite sand ((Ce, La, Th, Nd, Y)PO₄), a material rich in rare earth elements.

Ytterbium has few uses. It can be alloyed with stainless steel to improve some of its mechanical properties and used as a doping agent in fiber optic cable where it can be used as an amplifier. One of ytterbium's isotopes is being considered as a radiation source for portable X-ray machines.