Rare Metal

Also found in: Dictionary, Thesaurus.

rare metal

[′rer ′med·əl]
Any metal that is difficult to extract from ore and is rare and expensive commercially; includes masurium, alabamine, and virginium.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.

Rare Metal


a conventional name for any one of the more than 50 metals shown in Table 1. These metals are either relatively new to technology or else have so far received only limited application. The scale of production and fields of application of these metals are continuing to expand. The term “rare metals” came into use in the USSR in the 1920’s; in other countries, these elements are sometimes referred to as less common metals. Most rare metals are not widely distributed and are often dispersed in the earth’s crust. The considerable technological difficulties encountered in the extraction and purification from source material explain the relatively late discovery, study, and technological application of rare metals.

The production of rare metals has been developing at an especially high rate since World War II. The metals are essential for such new fields of technology as high-speed aviation, rocket construction, electronics, and atomic power engineering. Of course, it is true that the term “rare metals” loses its original meaning as the production of and demand for these metals increase.

Table 1. Technical classification of rare metals
Group of the periodicsystemElementsGroup of rare metals
‘Germanium, selenium, and tellurium are arbitrarily classed as metals, although they are actually semiconductors
Table 1. Technical classification of rare metalsLight
Table 1. Technical classification of rare metalsRefractory
Table 1. Technical classification of rare metalsDispersed
IIITable 1. Technical classification of rare metalsRare-earth
Table 1. Technical classification of rare metalsRadioactive

A technical classification system for rare metals has been developed (see Table 1) based on similarities of physicochemical properties, production technology, and certain other indicators. This classification is arbitrary, since many elements can belong to more than one group. For example, Rb and Cs can be classed as either light or dispersed elements; the typical dispersed element Re is also a refractory metal; the typical refractory metals V and Hf are also dispersed elements; and Ti can be classed as either a refractory or a light metal.

Light rare metals have a low density (from 0.54 g/cm3 for Li to 1.87 g/cm3 for Cs) and are highly active chemically. They resemble light nonferrous metals (Al, Mg, Ca, Na) in both properties and methods of extraction.

Refractory rare metals are included among the transition metals of groups IV, V, VI, and VII of the periodic system; in the atoms of refractory metals the completion of electron d sub-shells takes place. Refractory metals are noted for their high melting points (from 1670°C for Ti to 3410°C for W) and their ability to form refractory metal-like compounds with a number of nonmetals. Examples are carbides, nitrides, suicides, bor-ides, and beryllides.

Dispersed rare metals generally exist in the form of isomorphic admixtures to the minerals of other elements and are extracted as by-products from the tailings of metallurgical and chemical production processes. For example, Ga is obtained during the production of alumina, A12O3, and In is extracted from the tailings of Zn and Pb production.

Rare-earth metals have highly similar chemical properties. They are found together in ores and separation is extremely complex. Extraction with organic solvents and ion-exchange processes are used for this purpose.

The group of radioactive metals includes metals occurring in nature (Fr, Ra, Po, Ac, Th, Pa, U) and those produced artificially (Tc, Np, Pu). Uranium and plutonium are the most valuable of this group because of their use in the production of nuclear energy.

Rare metals are usually present in small concentrations in ores, and the ores are often complex. Therefore, ore dressing and chemical processes of isolation, separation, and purification of rare-metal compounds are highly important in the technology of rare-metal extraction. As a rule, rare metals are not directly smelted from ore concentrates but are reduced by various methods from purified chemical compounds. The diverse methods widely used in the metallurgy of rare metals include reduction of oxides and salts by gases, carbon, or metals, thermal dissociation of compounds, electrolysis in aqueous and molten media, and vacuum, arc, electron-beam, and zone melting. In addition, the methods of powder metallurgy are now widely used for refractory metals.


Zelikman, A. N., and G. A. Meerson. Metallurgiia redkikh metallov. Moscow, 1973.
Khimiia i tekhnologiia redkikh i rasseiannykh elemenlov, vol. 2. Edited by K. A. Bol’shakov. Moscow, 1969.
Songina, O. A. Redkie melally, 3rd ed. Moscow, 1964.
Spravochnik po redkim metallam. (Translated from English.) Edited by V. E. Pliushchev. Moscow, 1965.
Filiand, M. A., and E. I. Semenova. Svoistva redkikh elemenlov, 2nd ed. Moscow, 1964.


The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.
References in periodicals archive ?
These rare metals - a group of roughly 50 that includes indium, rare earths and gallium - are produced in small quantities, often several thousands of tons annually or less; blended with other metals; and traded in back-room deals.
Lithium is a key rare metal used in batteries, glass, ceramics and as an additive to make aluminum.
According to Apple Insider, the SEC document revealed on May 21 shows that Liquidemetal and Apple have arranged for an extended exclusive license allowing Apple to use a rare metal in its upcoming products until the specified date.
Japan is planning to provide economic aid to countries with good reserves of rare metal resources, the business daily Nikkei has reported.
Alex King, the Executive Director of the US Critical Materials Institute remarked toward the close of the Symposium, "Canada clearly has the natural resources, mining and materials processing experience and passion to make a significant contribution to the global rare metals supply chain."
International Resource News-August 16, 2019--NRP Stone submits Letter of Interest for acquisition of Rare Metals and Gems Investors
Bridenstine told CNBC's "Squawk Alley" on Thursday that the moon could be abundant in these rare metals. 
It is organised along three segments: Magnequench, Chemicals & Oxides and Rare Metals.
Cabot Corporation has entered into a definitive agreement to sell its Specialty Fluids business to Sinomine Rare Metals Resources Co.
Compared to these approaches that utilize rare metals (such as ruthenium and rhenium), the use of earth abundant metals is "greener" and inexpensive, and has thus attracted much interest.