3 Rare Ear t h E le m en t s REE Exp la i ned The rar e e arth ele m en ts R EE are a gr o u p o f 1 7 che m i cal m et all ic el em ents whi ch ap p ear in the p erio d ic t ab le The gro u p c o n sist s o f the 1 5 lan than id e ele m ents al o n g w ith Y t tri u m and Scan d iu m The y sha re m an y si m il ar pr o p er t ies w h ich is wh y t h e y o ccu r to g e ther in g eo l o g ical d e p o sits Th e 1 7 REEs are fo u n d in all RE E d ep o sits b u t their d istrib u ti o n and c o n centrati o n s v ary They are re ferr ed t o as rare b ecause it is n o t c o m m o n t o fin d the m in co m m er cial l y v iab l e c o n centra tio n s RE Es g enerall y fall in t o o n e o f t w o c at ego ri es li g h t ra re earths L RE E an d h eav y rare e arth s HRE E wi th v ar y in g lev els o f us es an d dem an d RE E m in eral d epo sits are usu all y rich in either L REE o r HREE bu t ra rely c o n tain b o th in sig n ifi can t q u an tities In g e n eral the y ar e v i tal t o s o m e o f the w o rld s fast es t gro wing m ar ke ts cl ean energ y and hig h t echn o l o g y Rare Ear t h s Expe c t e d to be in Sh or t Supp ly in t he n ex t 15 y ea r s Neodymi um Eur opi um Ter b iu m Dys pr o si um Y t t r i um L ight Rare Ear t h s L an than u m L a Ceriu m Ce P rase o d y m iu m P r N eo d y m iu m N d Sa m ari u m S m Hea vy Rare Ear t h s Le s s co m m o n a n d more v alu ab le Eur o p iu m Eu Gad o li n iu m Gd Te rb iu m T b D y spr o siu m D y H o lm iu m H o Erb iu m Er Thu li u m T m Yt te rb iu m Yb L u te tiu m L u Yt triu m Y A c c o u n te d fo r 668 o f g l o b al d e ma n d i n 2010 Not e s Y t t r i um i s l i g ht e r t ha n t he l i g ht r ar e e ar t hs b ut i nc l ud e d i n t he h e av y r ar e e ar t h g r o up b e c au se o f i t s c he m i c al a nd p hy si c a l a ss o c i at i o ns wi t h he a v y r ar e e ar t hs i n na t ur al d e po si t s P r o m e t hi um i s a sy nt he t i c e l e m e nt w hi c h do e s no t o c c u r n at ur al l y and S c a nd i um s pr o pe r t i e s ar e q ui t e d i f f e r e n t f r o m t he o t he r R E E s E r n s t Y oung T e c h n o lo g y Min e r a ls T h e rar e e a r th s r a c e is o n Ap r il 201 1