Symbol : Rb
Atomic Number : 37
Rubidium Oxide Density : 4.0g/cm3
Rubidium is a soft, silver-white metal that belongs to the alkali metal group of chemical
elements. Like the other alkali metals (Lithium, Sodium, Potassium and Caesium) pure
Rubidium is extremely reactive and would combust on exposure to water or oxygen. Its
melting point is 39 degrees centigrade. It is therefore usually seen in compounds such as
rubidium oxide or rubidium carbonate.
Rubidium is not at present used to any great extent in battery technology. If sodium-ion
batteries were to take market share from lithium-ion batteries in future, small amounts of
rubidium and caesium have been shown to improve the performance of sodium-ion
batteries. Rubidium carbonate has multiple industrial uses, principally speciality glasses such
as fibre optic cables, telecommunications systems including an important role in GPS
systems, aircraft guidance systems, and night vision devices. There are also important uses
in medical equipment, for example coronary artery disease imaging and myocardial
perfusion imaging. i.e. assessing the blood flow to the muscular walls of the heart. Further
uses occur in atomic clocks where rubidium like caesium is very accurate. Quantum
computing makes use of rubidium. Since it is easily ionized, it might be used as a propellant
in ion engines on spacecraft.
Broadly where caesium is used, rubidium can also be used. The most common use for
caesium compounds is as caesium formate in a drilling fluid. They are also used to make
special optical glass, as a catalyst promoter, in vacuum tubes and in radiation monitoring
Rubidium oxide is typically found in hard rock pegmatites, usually in lepidolite, but also in
pollucite or zinnwaldite. Rubidium is an important mineral at International Lithium Corp’s
Raleigh Lake pegmatite deposits in Ontario, Canada. In that location ILC has found
appreciable amounts of rubidium in microcline, a feldspar which has the rubidium replacing
potassium forming a Rb-microcline. The chemical composition is Rubidium Aluminium
Silicate. The process for extraction can be similar to that used for caesium.
Worldwide the largest producer of rubidium has historically been Canada, while the largest
reserves are believed to be in Southern Africa (eg Zimbabwe and Namibia) and Canada.
There is also rubidium in USA, Russia, Afghanistan, Australia and China. There are small
concentrations in some brines, but on a much smaller scale than lithium.
The market for rubidium, as for caesium, is relatively opaque – especially in volume but also
price achieved and in what quantities. Price guides can currently be found on
www.metal.com. As at January 2023, the price is given there for 99%+ purity of rubidium
carbonate of RMB 8,250/Kg (which equates to USD 1,210,000 per metric tonne). By
comparison the price of 99.2% purity lithium carbonate at the same time was RMB 445,000
per metric tonne which equates to USD 65,700. This means that rubidium carbonate at that
time had a market price of 18.5 x the price of lithium carbonate.