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New Data on and Discreditation of "Texasite," "Albrittonite," "Cuproartiniter" "Cuprohydromag

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New Data on and Discreditation of American Mineralogist, Volume 67, pages 156-169, 1982 New data on and discreditationof "texasite," "albrittonite," "cuproartiniter" "cuprohydromagnesite,"and "yttromicrolite," with correcteddata on nickelbischofite, rowlandite,and yttrocrasite DoNelo R. Peecon Department of GeologicalSciences The Universily of Michigan Ann Arbor, Michigan 48109 Wrlu.r.rrr B. SrnauoNs,Jn. Department of Earth Sciences Universityof New Orleans New Orleans,Louisiana 70122 Eruc J. EssBNeexo E. Wu. HnrNnrcH Department of GeologicalSciences The University of Michigan Ann Arbor, Michigan 48109 Abstract Dataare presented which show that "texasite" and "albrittonite" exist only as synthetic phasesand that "cuproartinite"and "cuprohydromagnesite" are not knownto existin any form. "Yttromicrolite" is a heterogeneousmixture of yttrianmicrolite and tantalite. These five phaseshave therefore been discredited as minerals.Major parts of the descriptionsof the mineralsrowlandite, yttrocrasite, and nickelbischofitefrom Llano County, Texas shouldalso be revised. We conclude, among other things, that the formula of rowlanditeis stillin question,that yttrocrasite has not yet been definitively shown to bea memberof the euxenitegroup and that nickelbischofitedoes not occur at the OxfordQuarry, Llano County,Texas. It is suggestedthat procedures for accreditationof a newmineral should includedeposition of a type or cotypespecimen in matrix to a suitableinstitution in sufficientquantity for X-ray diffractionor chemicalanalysis, coupled with the complete manuscriptto be publishedat a later time. fntroduction Commissionon New Minerals and Mineral Names (Kato, written communication,1981). We have critically re-examined "texasite" (Crook, 1977a), "albrittonite" (Crook and Mar- Data on specificminerals cotty, 1978),nickelbischofite (Crook and Jambor, 1979),rowlandite (Crook et a\.,1978), yttrocrasite "Texasite" (Crook, 1977b), "yttromicrolite" (Crook, 1979), Crook (1977a)states that "texasite" (definedas "cuprohydromagnesite"and "cuproartinite" (Os- PrzOzSO+)is a "supergene alteration product of waldandCrook, 1979).Wefindthataspectsofallof primary rare-earthminerals" occurring in pegma- thesepapers are subjectto question.The resultsof tites of the Llano region of Texas. The primary our studiesas presentedas part of this paper led us parent minerals contain typical undifferentiated to recommendthat the minerals"texasite", "albrit- suites of rare-earth elements. That "texasite" tonite", "cuproartinite", "cuprohydromagnesite", shouldhave such an origin, and that Pr shouldbe so and "yttromicrolite" should be discredited. This highly concentratedas to represent>99.9% of the recommendationhas been approvedby the I.M.A. rare earth elementspresent is geochemicallyunrea- 0003-0M>v82l0r02-0156$02.00 156 157 sonable.We believe that the explanation for this is 10,000/1so that a changeof5 in the ratio represents simply that synthetic Pr2O2SOahas been described a change of only 100-200 ppm in the minor rare as though it were a natural material. earth element, differences to be expected in a Dr. John Haschke, a former faculty member of synthetic material rich in Pr. As the synthetic the Department of Chemistry, University of Michi- sample has been purified commercially (Research gan, synthesizeda number of rare-earth compounds Chemicals, Phoenix, Arizona) using advanced ion and donated samples to Peacor prior to Crook's exchangeprocedures to obtain high purity praseo- time of residence at The University of Michigan. dymium, it is unreasonablethat a natural process Among these was a container of crystals of Pr2 could achieve higher levels of purity. These data O2SO4(identical in appearanceto crystals of "texa- therefore demonstrate that the compositions of site") which served as the source of material for X- "texasite" and the synthetic Pr2O2SO4(which was ray crystallographic studies (Peacor, unpubl. data). synthesizedin the samelaboratory as the Pr2O2SOa This containerofcrystals could not be found subse- which is missing from Peacor's laboratory) show a quent to the publication of the description of "texa- close similarity. These data also verify that the site" by Crook, although other samples of material claimed by Crook to be naturally occurring Haschke's synthetic rare-earth compounds were "texasite" is indeed nearly pure Pr2O2SO+.The still present in Peacor's laboratory. This demon- incredibly high purity reflected in his analysescan- strates that crystals of this extremely rare com- not simply be ascribed to analytical error on what pound were available in the laboratory where the might actually be impure natural material. "texasite" was studied. This is at first sight a Second, the fact that Nd was not detected in remarkable coincidence, but it is compatible with either sample(and thus is present only at levels less our other direct evidence showing the equivalence than 200 ppm, see Table l) is especially notewor- of synthetic and natural materials. thy. Haschke notes (written communication, 1979) We submittedsamples of "texasite" (so identi- that "the probability of finding a texasite sample fied originally as such by Crook) for neutron activa- tion analysis, along with samplesof synthetic Prz- Table l. Data for neutron activation analyses of synthetic (Haschke's O2SO4obtained from John Haschke and said by Pr2O2SOa sample)and "texasite" (Crook's sample) him (written communication, 1979) to have been Rareearth activity ratios synthesizedwith the same starting source materials and as part of the same experiments as the Pr2O2 SOaoriginally given to Peacor. The analyseswere Synthetic "texasite" carried out by Mr. John Jones of the Michigan Memorial Phoenix Project, The University of Mich- PrlTb 2.12 2.06 Pr/Dy 4.1 't3.25.2 igan.Results are presentedin part in Table l. These PrlSm 16.8 results show that there are striking similarities between Crook's "texasite" and synthetic Pr2 Pr/Ce 5.4 9.4 Pr/Eu 8.8 14.2't4.0 O2SO4.In the following discussionwe emphasize: PrlLa 14.3 (1) generalsimilarities, (2) Nd/Pr ratios, and (3) Au and Ag values. EulDy 0.06 0.04 Sm/Dy 0.24 0.39 First, there are clear, general similarities between CelDy 0.76 0.55 the analyses of Crook's type "texasite" and Haschke's synthetic phase. DylTb 1.24 0.97 Where rare earth ele- Sm/Tb 0.30 0.38 ments are relatively high in one they are relatively EulTb 0.07 0.04 high in the other. There are some exceptions to this rule, but since the analyseswere obtained on excep- Estimatedabsolute concentrations (ppm)' tionally small samples, the differences are not un- reasonable.Where the differences are highest (for Au 222 l0 Ag not detected not detected PrlEu and Pr/Ce) "texasite" has a lower concentra- (<4) (.4) tion of a given element relative to praseodymium than the sampleobtained from Haschke. It is impor- Tb 450 450 Nd not detected not detected tant to recognize that the absolute values of ratios (<2oo) (<2oo) such as Pr/Tb or Pr/Eu are on the order of 1.000to 158 with the same Nd/Pr ratio as my synthetic sample ed stoichiometric value (19.53Vo)considering that . is so incrediblethat it must be excluded.The galenawas used as a standard for S, and consider- 'didymium' separation of (mixture of Nd and Pr) ing the accuracy of normal probe data and correc- into the rather pure elements (neodymium and tion proceduresat The University of Michigan. The praseodymium)is one of the interesting historical quoted weight percents for La2O3, Ce2O3, and eventsof lanthanidechemistry." This difficult sepa- Nd2O3(all less than 0.l0Vo) are below minimum ration is accomplishedusing ion exchangeresins. detectable limits, especially considering X-ray in- Repeatedexchange of progressively more diferen- terferences.This is further indicated by the fact that tiated fractions is necessaryin order to ultimately Nd was not detected in "texasite" by neutron achieve high resolution. Haschke therefore con- activation analysis, as emphasizedabove. In short, cludes that "attainment of the same resolution of these data show that Crook's reported analytical Nd and Pr in a natural system and in a chemical results are almost certainly erroneous. processingfacility is beyond belief." We further Dr. Haschke states (written communication, emphasizethat not only are Nd levels the same in 1979)that: "The lattice parametersand d spacings, both samples,but Nd is not detectedin the $texas- reported on page 1007 of American Mineralogist, ite" sample. Such differentiation of Nd relative to Vol. 62 are my data for Pr2O2SOa.However the I/16 Pr is not credible in a natural mineral. values are not." Haschke further emphasizesthat: Third, of even greaterinterest is the fact that gold "I have never given Mr. Crook permission to was detectedin both the "texasite" and synthetic publish any of my data or to use any statements Pr2O2SOasamples (Table 1). Suchlevels of gold in a attributed to me." Dr. Haschke also assertsthat rare-earth differentiated pegmatite mineral are un- other statementsattributed to him by Crook are not reasonable.Haschke synthesized his Pr2O2SOaun- correct. For example Haschke says that (written der hydrothermalconditions in gold capsulescon- communication.1979. in contrastto Crook's state- taining HNO3 at 15,000psi pressure and 500'C menton page1008 of AmericanMineralogist): ". (written communication. 1979). Such conditions I do not (and never have) attributed the existenceof could be expectedto yield low but variable concen- a pure praseodymium mineral to crystalline stabil- trations of gold as contaminantsin the run products. ity. The structuresof Nd2O2SOaandPr2O2SOa
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