A LANTHANIDE LANTHOLOGY (.pdf) - Davidson Physics

RESOURCESOther significant bastnasite deposits are known[4], e.g Wigu, Tanzania, and elsewhere inAfrica, but none are in commercial production.Certain igneous rocks, made by repeated processes of melting and recrystallization, caninclude minerals enriched in the lanthanides and yttrium. The Ln's can substitute in crystalstructures for a variety of large positive ions, not only those also triply charged, and can be foundin many complex mineral compositions. The reduction in ionic radius from La at the beginning ofthe Ln-series, to Lu at the end, can create a crystal structure change along the series and aseparation into light lanthanide and heavy-lanthanide counterparts.The light-lanthanide phosphate, Monazite, has a heavy-lanthanide analogue, Xenotime, bothof which are lanthanide resources with the Monazite being available in much larger quantities.Monazite is a common component in "heavy" beach sands and found throughout the world,particularly along coast lines in Australia, Brazil and India. This heavy mineral has been releasedfrom a primary source by weathering and concentrated, by wave-action over long periods of time,into placer deposits. In addition to beach sand deposits, Monazite is also found in high grade inlanddeposits such as the Mt. Weld intrusion near Perth in Western Australia.[5]Xenotime, an Yttrium-heavy-Ln phosphate, comes from Malaysia, Thailand or China. Bothphosphates are recovered as by-products of mining for other more economically dominantmaterials, titanium / zirconium and tin minerals respectively.Some minerals mined, for example, for their Uranium or Niobium content, can also serve aslanthanide sources. Uranium mines in Canada have supplied, as by-product, yttrium-enrichedconcentrates for further processing. Similar resources, complex heavy-element mineralizations, areknown in countries such as Brazil and Australia. A cerium-rich Loparite, (Ln,Na,Ca)(Ti,Nb)O 3 , iscurrently mined in Russia's Kola peninsula, adjacent to Finland, and supplies the bulk of the CISdemand for Ln's.[6]The Ln's, in geochernical environments, occur as Ln 3+ cations of ≈100 pm radius, i.e. comparablesize to Ca 2+ . If the charge disparity is balanced elsewhere, Ln's can partially replace the ubiquitousdivalent calcium. Some Ca phosphates, e.g. apatites where the Ln proportion is a percent or more,are potential lanthanide resources. If the parent phosphate is mined for fertilizer then theby-products provide a source of Ln's, e.g. the Kola peninsula apatite that complements Loparite asa Ln resource.[4] Economic Geology of the Rare Earth Elements, A.N.Mariano, Rev. Mineral., 1989, 21, 308[5] Mt. Weld Rare Earths Project, D. Kingsnorth, Aus.IMM Bull., 1992, 8, 13[6] Rare Earths Industry of Today in the Commonwealth of Independent States, V.D.Kosynkin et al., J. AlloysComp., 1993, 192, 11834