Cesium, or caesium, is an alkali metal and one of the five metals that are liquid near room temperature. The others are mercury, francium, gallium, rubidium, and bromine. Caesium is used in the oil industry as a drilling fluid, and it is also used in atomic clocks. Caesium is extremely pyrophoric, and the most electropositive of all the stable elements. It is found in pegmatite ores in the mineral pollucite.
Domestic Production and Use: Pollucite, the principal ore mineral of cesium, is not mined in the United States; however, occurrences of cesium-bearing pollucite in pegmatites have been discovered in Maine and were mined in the past. Pollucite occurs in zoned pegmatites worldwide, associated with lepidolite, petalite, and spodumene; the largest deposit is at Bernic Lake in Canada. Canada is the leading producer and supplier of pollucite concentrate, which is imported for processing by one company in the United States. The principal end use of cesium is in formate brines, a high-density, low-viscosity fluid used for high-pressure/high-temperature (HPHT) oil and gas drilling and exploration. Cesium formate possesses anti-oxidant and water-structuring properties that protect drilling polymers from thermal degradation and has the required density needed to maintain well control. Other significant end uses are in biomedical, chemical, and electronic applications. Cesium is used as an atomic resonance frequency standard in atomic clocks, playing a vital role in global positioning satellite, Internet, and cell phone transmissions and aircraft guidance systems. Cesium clocks monitor the cycles of microwave radiation emitted by cesium’s electrons and use these cycles as a time reference. Owing to the high accuracy of the cesium atomic clock, the international definition of a second is based on the cesium atom. The U.S. primary time and frequency standard is based on a cesium fountain clock at the National Institute of Standards and Technology in Boulder, CO. Cesium-131 and cesium-137 are used primarily to treat cancer. Both have been used in brachytherapy, where the radioactive source is placed within the cancerous area. With a shorter half-life and higher energy, cesium-131 is used as an alternative to iodine-125 and palladium-103 in the treatment of prostate cancer. Cesium-137 is also widely used in industrial gauges, in mining and geophysical instruments, and for sterilization of food, sewage, and surgical equipment. Cesium can be used in ferrous and nonferrous metallurgy to remove gases and other impurities.
Salient Statistics—United States: Consumption, import, and export data for cesium have not been available since the late 1980s. Because cesium is not traded, no market price is available. Consumption of cesium in the United States is estimated to be only a few thousand kilograms per year. In 2010, one company offered 1-gram ampoules of 99.8% (metals basis) cesium for $52.00 each and 99.98% (metals basis) cesium for $64.00, an increase of 2.6% and 1.9% from that of 2009, respectively. The price for 50 grams of 99.8% (metals basis) cesium was $642.00, and 100 grams of 99.98% (metals basis) cesium was priced at $1,760.00, an increase of 2.1% and 2.0% from that of 2009, respectively.
Recycling: Cesium formate brines are normally used by oil and gas exploration clients on a rental basis. After completion of the well, the used cesium formate is returned and reprocessed for subsequent drilling operations. Approximately 85% of the cesium formate can be retrieved and recycled for further use. There are no data available on the amounts used or recovered.
Import Sources (2006–09): Canada is the chief source of pollucite concentrate imported by the United States, and the United States is 100% import reliant.
Events, Trends, and Issues: Domestic cesium occurrences will remain uneconomic unless market conditions change, such as the discovery of new end uses or increased consumption for existing end uses. Commercially useful quantities of inexpensive cesium are available as a byproduct of the production of lithium. Increases in lithium exploration are expected to yield discoveries of additional cesium resources, which may lead to expanded commercial applications. There are no known human health issues associated with cesium, and its use has minimal environmental impact. Cesium’s cost and reactivity limit its viability in many applications; however, its use in cesium formate brines and nuclear medicine is showing steady growth. Cesium formate drilling operations are being undertaken in the Thar Desert in Pakistan, in the North Sea off the coast of Norway, and in Argentina. In addition to its use in drilling fluid, cesium formate brine is used as a fast-acting liquid pill for releasing drill pipes differentially stuck in oil-based mud (OBM) filter cakes. The pill of formate brine rapidly destroys the OBM filter cake and allows the pipe to be jarred free.
The International Atomic Energy Agency has indicated that cesium-137 is one of several radioactive materials that may be used in radiological dispersion devices or “dirty bombs.” Cesium-137 is now regulated in the United States by the U.S. Nuclear Regulatory Commission (NRC) and the Environmental Protection Agency (EPA). The NRC monitors devices containing cesium-137, requiring material holders to obtain specific licenses for these devices. The EPA places a maximum allowance of cesium-137 that can be released into the air by nuclear facilities and requires the cleanup of contaminated soil and groundwater. The NRC agreed to encourage research into finding and implementing alternatives, but deemed that a near-term replacement was not practical and would be detrimental to current emergency medical capabilities.
World Mine Production and Reserves: Pollucite, mainly formed in association with lithium-rich, lepidolite-bearing or petalite-bearing zoned granite pegmatites, is the principal cesium ore mineral. Cesium reserves are therefore estimated based on the occurrence of pollucite, which is mined as a byproduct of the lithium mineral lepidolite. Most pollucite contains 5% to 32% Cs2O. Data on cesium resources and mine production are either limited or not available. The main pollucite zone at Bernic Lake in Canada contains approximately 400,000 metric tons of pollucite with an average Cs2O content of 24%, and a secondary zone of approximately 100,000 metric tons of pollucite contains an average of 5% Cs2O. The next largest occurrence that may become economic is in Zimbabwe.
World Resources: World resources of cesium have not been estimated. Cesium is associated with lithium-bearing pegmatites worldwide, and cesium resources have been identified in Namibia and Zimbabwe. Smaller concentrations are also known in brines in Chile and China and in geothermal systems in Germany, India, and Tibet.
Substitutes: Cesium and rubidium can be used interchangeably in many applications because they have similar physical properties and atomic radii. Cesium, however, is more electropositive than rubidium, making it a preferred material in many applications.
Cabot Corporation (NYSE: CBT) – http://www.cabot-corp.com/Cesium-Fine-Chemicals – Their Tanco Mine in Bernic Lake, Manitoba, Canada has the world’s largest deposit of pollucite and is the largest producer of caesium. The company produces cesium carbonate, cesium fluoride, cesium hydroxide, cesium sulfate, cesium chloride, cesium formate, and cesium nitrate.
Consolidated Abaddon Resouces (CVE: ABN)
American Elements – http://www.americanelements.com/cs.html – Cesium acetate, cesium azide, cesium bromide, cesium carbide, cesium carbonate, cesium chloride, cesium dichromate, cesium fluoride, cesium fluoroaluminate, cesium hydrogencarbonate, cesium hydroxide monohydrate, cesium iodide, cesium metavanadate, cesium methanesulfonate, cesium nitrate, cesium orthovanadate, cesium oxalate, cesium oixde, cesium perchlorate, cesium permanganate, cesium phosphide, ceisum propionate, cesium selenide, and cesium sulfate, cesium telluride, cesium tetrachloroaluminate, cesium tetraphenylborate, cesium titanate, cesium tribromide, and cesium triiodide.
IsoRay (AMEX: ISR) – Cesium-131 brachytherapy treatment