Caesium Mining

Caesium Mining:

Caesium or cesium is an alkali earth metal found on the earth's crust. It is noticed in many ores as both small and major composites. It is mined about 10 to 30 tons at some selective places on the world.

Ores:

The ores bearing caesium are sylvite (KCl), carnallite (KMgCl3?6H2O), beryl (Be3Al2(SiO3)6), avogadrite ((K,Cs)BF4), pezzottaite (Cs(Be2Li)Al2Si6O18), londonite ((Cs,K)Al4Be4(B,Be)12O28), rhodizite, pollucite (Cs(AlSi2O6)), lepidolite and petalite. From the above ores, only pollucite is used for the commercial production of caesium because other ores have very small composition of caesium comparing to pollucite which contains an average of 24% in it.

Mining of ore:

Pollucite, the chief caesium ore is mined by underground mining only. The ore is mined by drilling large tunnels in the surface of the earth. In this mining process the waste materials produced is much lesser than surface mining and has lesser health hazards for labors. It employs more number of labors and machineries. The ore are mostly deposited deep below 100m.

Tanco mine in Canada is the largest caesium mining mine with 75% of world's caesium production coming from it. USA depends solely on Tanco mine for its 100% caesium demands.

Processing and extraction:

The extraction of caesium metal from the collected pollucite ores are executed by methods namely direct reduction, electrolysis and acid digestion. But before doing any of those methods the mined ores are crushed initially. The crushed ore then sorted out by manual labor. Here, hand sorting of the crushed ore is employed because the ore pollucite are mostly present in pegmatites which are indigenous rocks with mixture of quartz and other ore particles. The pollucite is carefully separated from the mixture and are grinded.

Acid digestion:

The grinded small particles are dissolved in strong acids like hydrochloric acid (HCl), sulfuric acid (H2SO4), hydrobromic acid (HBr) or hydrofluoric acid (HF). In reaction with the HCl the pollucite ore produces soluble chlorides along with insoluble chlorides double salts of caesium as caesium antimony chloride (Cs4SbCl7),caesium iodine chloride (Cs2ICl), or caesium hexachlorocerate (Cs2(CeCl6)).

From the reaction the insoluble caesium salts are separated and made to precipitate where pure double salts are decomposed and Caesium chloride is collected as precipitate by evaporating the water. Then the resultant caesium chloride is reduced into metal by potassium, sodium or calcium in vacuum atmosphere. In the case of sulfuric acid the insoluble double salts produced are caesium alum (CsAl (SO4)2?. 12H2O) which is directly reduced into caesium metal by sodium, potassium or calcium in vacuum.

Direct reduction:

The caesium chloride or caesium halides which are directly obtained from the pure components of ore can be reduced into caesium metal. The reduction process is done with calcium or barium at the temperature of 700 to 800 ?. This method can only applied when pure components are present in the ores initially.

Electrolysis:

In electrolysis, a high quality gas-free pure caesium can be produced. At first the collected grinded ore is converted into caesium cyanide. After that, caesium cyanide undergoes electrolytic process having cathode and anode in which the caesium fused with the cyanide is extracted and sucked out in a vacuum atmosphere producing pure metal.

The world's most caesium production is done in Canada at the Tanco mine near the Bernic Lake and apart from that Bikita in Zimbabwe and Karibib Desert in Namibia.

Definition:

Cesium is not mined in the United States. Pollucite, the principal ore mineral of cesium, is imported as focus from Canada by one company in the United States. There are occurrences of pollucite in pegmatites in South Dakota and Maine. Because of its high density, the main utilize of cesium is in the manufacture of specialty, high-density drilling fluids used in the global oil and gas exploration industry.

Application:

Caesium is used as a catalyst in the hydrogenation of limited organic compounds.
Radioactive isotopes of caesium are used in the medical field to treat certain types of cancer.
Caesium fluoride is extensively used in organic chemistry as a base and as a source of anhydrous fluoride ion.