Caesium and Rubidium

Lepidico’s strategy is to develop its Phase 1 Project with a US nexus associated with supply of specialty alkali metal chemicals that are designated as Critical Minerals by the US Government. This has led to the United States International Development Finance Corporation (DFC) providing Lepidico with an indicative, non-binding term sheet in respect of debt funding for the Phase 1 Project in Namibia, along with a formal mandate being agreed for DFC to undertake an in-depth analysis and evaluation of the Karibib Phase 1 Project for the purpose of determining whether it qualifies for DFC financing.

  • Inaugural Ore Reserve of 6.7 million tonnes grading 0.46% Li2O, 0.23% rubidium and 320ppm caesium is believed to be the world’s only Code compliant estimate for the strategic alkali metals caesium and rubidium.

The Phase 1 Plant is designed to produce caesium formate but can be adapted to produce alternative caesium compounds. Rubidium will be produced as Rubidium Sulphate.

Caesium formate production from the Phase 1 Plant will be approximately 260tpa over the first ten years of production. Caesium formate will be produced as a clear liquid brine with a specific gravity of 2.2.

Rubidium sulphate production will vary between 1400 – 1600 tonnes per annum

Production planned from the existing JORC Code compliant Ore Reserve Estimate provides an initial 14 year producing life. This is understood to be the only Code compliant Ore Reserve of caesium and rubidium globally

Caesium Compounds

Caesium sulphate is commonly used in chemical catalysts to enhance the production efficiency of sulphuric acid. Caesium hydroxide and/or carbonate are also used in petrochemical catalysts.  Caesium iodide is largely used in fluoroscopy equipment—Fourier-transform infrared spectrometers—as the input phosphor of x-ray image intensifier tubes, and in scintillators. Cesium bromide is used in infrared detectors, optics, photoelectric cells, scintillation counters, and spectrophotometers

Caesium Formate is used in the oil industry along with other formate brines as well completion fluids.


Rubidium can substitute for caesium in a number of industrial applications, particularly catalysts and those that rely on the photoemissive properties of these metals.

Applications for rubidium and its compounds include biomedical research, electronics, specialty glass, and pyrotechnics. Specialty glasses are the leading market for rubidium; rubidium carbonate is used to reduce electrical conductivity, which improves stability and durability in fibre optic telecommunications networks.

Biomedical applications include rubidium salts used in antishock agents and the treatment of epilepsy and thyroid disorder; rubidium-82, a radioactive isotope used as a blood-flow tracer in positron emission tomographic imaging; and rubidium chloride, used as an antidepressant.

Rubidium atoms are used in academic research, including the development of quantum-mechanics-based computing devices, a future application with potential for relatively high consumption of rubidium. Quantum computing research uses ultracold rubidium atoms in a variety of applications.

Rubidium’s photoemissive properties make it useful for electrical-signal generators in motion-sensor devices, night-vision devices, photoelectric cells (solar panels), and photomultiplier tubes.

Rubidium is used as an atomic resonance- frequency-reference oscillator for telecommunications network synchronization, playing a vital role in global positioning systems. Rubidium-rich feldspars are used in ceramic applications for spark plugs and electrical insulators because of their high dielectric constant.

Rubidium hydroxide is used in fireworks to oxidize mixtures of other elements and produce violet hues.

The U.S. military frequency standard, the United States Naval Observatory (USNO) timescale, is based on 48 weighted atomic clocks, including 4 USNO rubidium fountain clocks.