Geochemistry and Main Uses of Minerals - Thanatia: The Destiny of the Earth's Mineral Resources - page 543

B.2.53 Rubidium
Rubidium is a silvery white, very active metal as are the other alkali metals. Al-
though very abundant, no pure Rb-containing mineral is known. Much of the com-
mercially available material is obtained as a byproduct of lepidolite processing for
Li. It occurs naturally in the minerals pollucite, lepodite, carnallite, zinnwaldite
and leucite.
Rubidium and its salts have few commercial uses. The metal is used in the
manufacture of photocells and in the removal of residual gases from vacuum tubes.
Rubidium salts are used in glass and ceramics and in fireworks to give them their
purple colour.
B.2.54 Ruthenium
Ruthenium is one of the rarest metals on Earth. It is either found in its native form
or associated with platinum, osmium and iridium. Like the other platinum metals,
it is commercially extracted from nickel and copper deposits. It finds use in the
electronic and chemical industries, with smaller amounts being used in alloying in
order to increase hardness and corrosion resistance. It is also employed in electrical
contact alloys and filaments, in jewellery, in pen nibs and in instrument pivots. Like
the other metals of its group, it is a versatile catalyst used in different industrial
processes.
B.2.55 Samarium
Samarium is used to produce permanent magnets with cobalt. Whilst they are not
as strong as NdFeB permanent magnets they are still very much used. Notwith-
standing SmCo magnets can work at higher temperatures (>700 C) without los-
ing coercitivity. Samarium is also used in special X-ray lasers for analytic equipment
and military applications. It easily absorbs neutrons and is subsequently used in
nuclear power plants in fission controlling rods. In medical applications samarium
(II) iodide is used for the development of anticancer drugs whilst samarium-153
derivatives form part of radiopharmaceuticals for the treatment of metastatic bone
pain. Samarium induces superconductivity. The discovery of a new family of high-
temperature (56 K) superconductors based on samarium-doped SrFeAsF opens
the window for future demand. Samarium is estimated in the short term (by 2015)
to have only a 2% share of world REE supply.
For more details see Sec. B.2.50.
B.2.56 Scandium
Scandium occurs in many ores in trace amounts, but has not been found in su cient
enough quantities to be considered a reserve. Therefore, scandium has been pro-