MEI Online recently added Rare Earths to the Metallic Ores Commodity pages.
The question is - what is a rare earth metal, or what is not a rare earth metal? The latter question was asked recently in a posting on the Rare Metal Blog.
The general consensus, both in that discussion, and elsewhere, is that the rare earth metals include the 15 lanthanoid elements and one or both of the elements yttrium and scandium.
Why am I concerned? My book Mineral Processing Technology was first published in 1979, the latest, 7th, edition in 2006. The Introductory chapter of every issue has contained the sentence "It is interesting to note that the so-called common metals, zinc and lead, are less plentiful than the rare-earth metals (cerium, thorium, etc.)".
Cerium is definitely a rare earth metal, but thorium? Have I been wrong all these years? The reason for the error, if there is one, is lost in the mists of time, but I suspect that the mineral monazite was to blame- the main source of thorium and often referred to as a rare earth phosphate.
I am going to assume that I was wrong, and change the commodity entry to rare earths and thorium!
Monday 25 January 2010
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From Gareth Hatch, Dexter Magnetic Technologies, Inc., USA
ReplyDeleteBarry: while thorium is not a rare earth metal, you're right that it frequently occurs together with the rare earths, in monazite particularly but also in other minerals.
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