New Mexico Mineral Symposium — Abstracts

The rare-earth elements (REE) include a group of 15 chemically similar elements called the lanthanide group (La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu). Yttrium (Y) is included in this group because it has chemical properties similar to the REE and it typically occurs with them. REE are found in more than 100 minerals, but significant concentrations are rare.

Five types and examples of REE deposits recognized in New Mexico are: 1) veins and breccias (Laughlin Peak, Colfax County), 2) pegmatites (Harding Pegmatite, Taos County), 3) carbonatites and alkalic rocks (Lemitar Mountains, Socorro County), 4) Cretaceous heavy-mineral, beach-placer deposits (Sanostee, San Juan County), and 5) Recent stream-placer deposits. REE minerals also are found in numerous other types of deposits and host rocks but not in economic concentrations. Economically, the most significant deposits in the state are found in veins and breccias; however, REE-bearing minerals can be found in any of the deposit types. The only production of REE from New Mexico, although not significant, has come from pegmatites and from the Gallinas Mountains, Lincoln County. However, Molycorp, Inc. recently announced it will develop the Pajarito Mountain deposit, Otero County, and mine eudialyte for Y and Zr; eudialyte occurs in Precambrian nepheline syenite. Other favorable areas for development include Laughlin Peak, Colfax County, and the Gallinas Mountains, Lincoln County, both vein and breccia deposits.

Some of the REE minerals form attractive specimens and are collected by mineral collectors. Point of Rocks Mesa, Colfax County, although not an REE deposit, has yielded micromounts of eudialyte, mosandrite, steenstrupine, and tundrite. No doubt other REE-bearing minerals will be collected from this locality. Bastnaesite from the Gallinas Mountains, Lincoln County, is well known to collectors. Many of the pegmatites in New Mexico have yielded REE minerals such as betafite, zircon (cyrtolite), euxenite, senotime, and others. Zircon, monazite, and garnet are common in Recent stream-placer deposits. A list, complete for New Mexico, of REE minerals and minerals that may contain REE as impurities are:
(*species reported new to New Mexico since Northrop, 1959)

aeschynite (Ce,Ca,Nd,Y,Fe,Th)(Ti,Nb)₂(0,0H)₆
*agardite (Y,Ca)Cu₆(AsO₄)₃(OH)₆•3H₂0
allanite (Ce,Ca,Y)₂(Al,Fe⁺³)₃(SiO₄)₃(OH)
apatite group Ca₅(PO₄)₃(F,Cl,(OH)) ± REE
bastnaesite (Ce,La)(CO₃)F ± U,Th
betafite (Ca,Na,U)₂(Ti,Nb,Ta)₂O₆(OH) ± Fe,REE
brannerite (U,Ca,Ce,Y)(Ti,Fe)₂O₆
*brockite (Ca,Th,Ce)(PO₄)•H₂0
*chernovite-(Y) YAsO₄
*chevkinite (Ce,Ca,Th)₄(Fe⁺²,Mg)₂(Ti,Fe⁺³)₃Si₄O₂₂
*crandalite CaAl₃(PO₄)₂(OH)₅•H₂0
eudialyte Na₄(Ca,Ce)₂(Fe,Mn,Y)ZrSi₈O₂₂(OH,Cl)₂ ± REE
euxenite-(Y) (Y,Ca,Ce,U,Th)(Nb,Ta,Ti)₂O₆
fergusonite (Y,La,Ce,Nd)(Nb,Ta)O₄ fluorite CaF₂ ± REE
gadolinite-(Y) Y₂Fe⁺²Be₂Si₂O₁₀
garnet (Ca,Fe⁺²,Mg,Mn⁺²)₃(Al,Cr⁺³,Fe⁺³,Mn⁺³,Si,Ti,V⁺³,Zr)(SiO₄)₃ *
gasparite CeAsO₄
monazite (Ce,La,Nd,Th)PO₄
*mosandrite (rinkite) (Na,Ca,Ce)₃Ti(SiO₄)₂F
samarskite-(Y) (Y,Ce,U,Fe)₃(Nb,Ta,Ti)₅O₁₆
*steenstrupine-(Ce) Na₁₄Ce₆Mn⁺² Mn⁺³ Fe₅²⁺ (Zr,Th)(SO₁₈)₂(PO₄)₇•3H₂0
*thorbastnaesite Th(Ca,Ce)(CO₃)₂F₂•3H₂0
Titanite CaTiSiO₅
*tundrite-(Nd) Na₃(Nd,La)₄(Ti,Nb)₂(SiO₄)₂(CO₃)₃O₄(OH)•2H₂0
uraninite UO₂ ± REE,Th,Y,Pb
*xenotime-(Y) YPO₄
yttrotantalite-(Y) (Fe⁺²,Y,U)(Nb,Ta)O₄
zircon (cyrtolite) ZrSiO₄
*zirkelite (Ca,Th,Ce)Zr(Ti,Nb)₂0₇