Rubidium is a soft, silver-white metal that belongs to the alkali metal group of chemical elements. It is represented by the symbol Rb, and it has the atomic number 37. 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, and night vision devices. There are also uses in medical equipment and atomic clocks. Quantum computing makes use of rubidium.
Rubidium is typically found in hard rock pegmatites, usually in lepidolite, but also in pollucite or zinnwaldite. The process for extraction can be similar to that used for caesium. Rubidium oxide is an important mineral at International Lithium Corp’s Raleigh Lake pegmatite deposits in Ontario, Canada.
Worldwide the largest producer of rubidium has historically been Canada, while the largest reserves are believed to be in Southern Africa and Canada. There is also rubidium in USA, Russia and Afghanistan. There are small concentrations in some brines, but on a much smaller scale than lithium.
The market price of 99.75% rubidium carbonate, the most widely used rubidium chemical, was around US$ 57 for 10 grams in 2019 (i.e. US$ 5,700 per kilogram). This is considerably higher, by several hundred times, than the price for Lithium or Potassium Carbonate.
Comparative prices of Lithium, Rubidium and Caesium. Source: SMM (https://www.metal.com/), May 24, 2021.
|Product||Price (USD)||Price Ratio to Lithium Carbonate|
|Lithium Metal (Li≥99%)||$97,331/tonne ($97/kg)|
|Lithium Carbonate (99.5% Battery Grade)||$13,971/tonne ($13.97/kg)||1|
|Caesium (Cs≥99.5%)||$109.89/g ($109,890/kg)|
|Rubidium (Rb≥99.5%)||$125.60/g ($125,600/kg)|
|Rubidium Carbonate (Rb2CO3≥99%)||$1,059.65/kg||75.9|