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Wakefieldite ((La,Ce,Nd,Y)VO4) is an uncommon rare earth element vanadate mineral. There are four main types of wakefieldite- wakefieldite-(La), wakefieldite-(Ce), wakefieldite-(Nd), and wakefieldite-(Y), depending upon the dominant rare earth metal ion present. Wakefieldite has a Mohs hardness ranging from 4-5.〔The Mineral and Locality Database, (''Wakefieldite-(La)'' ).〕 Wakefieldite forms crystals of tetragonal structure. In terms of crystal structure, it is the vanadate analog of the rare earth phosphate mineral xenotime. Unlike xenotime, it is more favorable for wakefieldite to contain the lighter rare earth elements over the heavier ones. Due to the lanthanide contraction, the heavier rare earths have smaller ionic radii than the lighter ones. When the phosphate anion is replaced by the larger vanadate anion, the tetragonal crystal system preferentially accommodates the larger light rare earth elements.〔Miyawaki R., and I. Nakai. (1996). "Crystal Chemical Aspects of Rare Earth Minerals." Ed. Andrian P. Jones, Frances Wall, and C. Terry Williams. ''Rare Earth Minerals: Chemistry, Origin and Ore Deposits.'' London: Chapman & Hall. (p 29-30).〕 Wakefieldite was first described for an occurrence in the Evans Lou mine, St. Pierre de Wakefield, Quebec, Canada〔Miles, Norman M., et al., ''Wakefieldite, Yttrium Vanadate, a New Mineral From Quebec,'' American Mineralogist, Vol 56, Mar.-Apr. 1971 http://www.minsocam.org/ammin/AM56/AM56_395.pdf〕 and later designated Wakefieldite-(Y).〔http://www.mindat.org/min-4234.html Mindat, Wakefieldite-(Y)〕 Wakefieldite-(Ce) was first described as ''kusuite'' for its type locality in the Kusu deposit, 85 km SW of Kinshasa, Zaire. It was renamed in 1977 as the Ce analog of wakefieldite-Y.〔http://rruff.geo.arizona.edu/doclib/hom/wakefielditece.pdf Handbook of Mineralogy, Wakefieldite-(Ce)〕 Wakefieldite-(La) was first described in 2008 for an occurrence in the Glücksstern mine, Gottlob Hill, Friedrichroda, Thuringia, Germany.〔http://www.webmineral.com/data/Wakefieldite-(La).shtml Webmineral data, Wakefieldite-(La)〕 Wakefieldite-(Nd) was first described in 2008 at the Arase mine, Kami city, Kochi Prefecture, Shikoku Island, Japan.〔http://www.mindat.org/min-38894.html Wakefieldite-(Nd)〕〔Discovery of wakefieldite-(Nd), a new rare earth mineral, Moriyama,T., et al., http://unit.aist.go.jp/georesenv/english/result-e/ten-big-news/2008/2008-1-2.pdf〕 ==References== 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Wakefieldite」の詳細全文を読む スポンサード リンク
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