Background | Name | Sources | Uses | Substitutes and Alternative Sources
Rubidium is a very soft, silvery-white metallic element. Its atomic number is 37 and its symbol is Rb. Rubidium was discovered in 1861 by the German chemists, Robert Bunsen and Gustav Kirchhoff. It is the 16th most abundant element in the Earth’s crust (making rubidium a pretty common element). It belongs to a group of elements known as the alkali metals, such as sodium, potassium, cesium and lithium. Like the other alkali metals, rubidium reacts violently with air and water. When exposed to air, it bursts into flame. When put in water, it explodes. Its melting point is so low (103 degrees F, 40 degrees C) that it will melt on a very hot day. Scientists know that rubidium stimulates the metabolism. However, it is not known whether rubidium is beneficial to health. Rubidium does not combine with other elements or ions to create minerals. It is found, though, in trace amounts in the minerals that contain essential amounts of other alkali metals. These include the cesium and potassium rich zeolites, pollucite and leucite, and the lithium rich mica, zinnwaldite (a variety of the mineral lepidolite). One isotope of rubidium is radioactive. Because it is impossible to separate this isotope from non-radioactive rubidium, nearly all processed rubidium is slightly radioactive.