rare earth

noun

any element of the lanthanide series (atomic numbers 57 through 71) (Freq. 1)

• Syn: ↑rare-earth element, ↑lanthanoid, ↑lanthanide, ↑lanthanon

• Hypernyms: ↑group, ↑grouping

• Hyponyms: ↑terbium metal

* * *

noun

1. : any of a group of very similar oxides of metals or a mixture of such oxides that occur together often associated with thorium in widely distributed but relatively scarce minerals (as monazite, bastnaesite, xenotime, gadolinite) and that are separated only with difficulty (as by fractional crystallization or by ion exchange)

2. or rare-earth element or rare-earth metal : any of the series of metallic elements whose oxides are the rare earths, which include the fourteen elements following lanthanum through lutetium with atomic numbers 58 through 71, usually lanthanum itself, and according to some yttrium and even scandium, which are chiefly trivalent, and which except for lanthanum, lutetium, yttrium, and scandium form paramagnetic salts in many cases colored — symbol RE; compare cerium metal, lanthanide, periodic table, yttrium metal; element table

* * *

Chem.

the oxide of any of the rare-earth elements contained in various minerals.

[1875-80]

* * *

rare earth noun

1. An oxide of a rare-earth element, any of a group of metallic elements (some of them rare) closely similar in chemical properties and very difficult to separate

2. Now more usu a rare-earth element itself

• • •

Main Entry: ↑rare

* * *

rare earth,

1. an oxide of a rare-earth element: »

Rare earths can be used in control rods for nuclear reactors, and also as a radiation shielding ingredient in concrete (Science News Letter).

2. = rare-earth element. (Cf. ↑rare-earth element)

rare-earth «RAI URTH», adjective.

of or having to do with rare earth.

* * *

(also rare earth element or rare earth metal) n. Chemistry any of a group of chemically similar metallic elements comprising the lanthanide series and (usually) scandium and yttrium. They are not esp. rare, but they tend to occur together in nature and are difficult to separate from one another