Rbe6(Podo(OH)E, a NEW MINERAL SPECIES from THE
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Canadian Mineralogist Vol. 23, pp. 4346 (1985) TIPTOPITE(Li,K,Na,Ga,n)rBe6(POdo(OH)e, A NEW MINERALSPECIES FROM THE BLACKHILLS, SOUTH DAKOTA JOELD. GRICE Mineral SciencesDivision, NationalMuseum of Natural Sciences,Ottawa, Ontario KIA 0M8 DONALD R. PEACOR Depdrtmentof GeologicalScienca, IJniversityof Michigan,Ann Arbor, Michigan48109, U,S.A. GEORGE W. ROBINSON AIN JERRY VAN VELTHUIZEN Mineral SciencesDivision, National Museumof Natural Sciences,Ottawa, Ontario KIA 0M8 WILLARD L. ROBERTS ANDTHOMAS J. CAMPBELL Museumof Geotogl, SouthDakota Schoolof Mines and Technolog, Rapid City, SouthDakota 57701'U.S-A. PETE J. DUNN Departmentof Mineral Sciences,Smithsonian Institution, Washington, D.C, 20560,U.S.A. poudres) en ABSTRACT tion X les plus intenses(m6thode des [d Aoxmot sont:3.8 I (40X120),3.65(4Xl I l)' 3.36(s0X030)' Tiptopite is a new mineral specic from the Tip Top mine, 2.966(100)(12r),2.525(90X040), 2.348(70)(002)' near Custer, South Dakota. It occurson massiveberyl in 2.223(60)(04r),2.0'77 (s0)(23r), 1.943(40)(330)et a phosphatepegmatite as a secondarymineral associated 1.606(40\(142).Les analyses par microsonde 6lectronique' with roscherite, fransoletite, montgomeryite and englishite. absorptionatomique et thermogravim6trieont donn6(en It forms clear, colorless,lustrous, radial aggregatesof elon- poids):Li2O 4.5, Na2O 6.1, K2O 9'9, BeO 15.l'-CaO- 4.3' gate hexagonalprisms up to 0.1 x 0. I x 2.0 mm. It is Mno o.zfanro30.3; P2o5 55.1, H2o 3.4'total 98.9. La brittle with an uneven fracture. The measured density is formule peut s'6crire (Li2.6sK1.67Na1.75Cag.68 2.65Q) e/cm3. Optically it is uniaxial positive, <,r1.551(l) Mne.qrsT.ss(Be5.36Pe.57A16.q5)_re.ooPe_.oopzr.sz[(OH):.:z and e 1.559(l).It is hexagonal,with popsiblespace-group eo))o jii.r, <iuideaiement, d'aprbs la densitdobserv6e, P63/m or P63,a 11.655(5),c 4.692(2)it, andZ = l. The (Li,K,Na,Ca," ! )sBe6P6024(0H)4. in the powderpattern strongeslten X-ray-diffraction lines Mots-cl6s:tiptopite, nouvelle espbce min6rale, Dakota du are: 3.81(40)(120),3.6s(40)(111), Id in A0X,r01 Sud,phosphate' Pegmatite. 3.36(50)(030), 2.966(100)(l2l). 2.525(e0)(040), 2.348(70)(002), 2.223(60)(04r), 2.077(s0)(231), 1.943(40X330) and I .606(40)(142). The combined results INrnooucrtoN of electron-microprobe,atomic absorption and thermal The Tip Top mine occursin one of many geologi- gravimetric analysesgive: Li2O, 4.5, Na2O 6.1, K2O 9.9, cally relatedphosphate-rich pegmatites in the Black BeO 15.1,CaO 4.3, MnO 0.2,Al2O3,0.3, P2O5 55.1, H2O Hills of South Dakota. During mining operationsfor yields formula 3.4, sum 98.9 wt.9o, which the beryl during the winter of 1981-1982'fracture fillings (Liz.eaKt.rz Na1.75Cae.66Mn6.6)p7.s0(Be5.36Po.srAb.os)re.ooof interesting and beautiful secondaryphosphate (POa)6.35]s3.72or, ideally, Po.ooOzr.sz[(OH):.:r were encountered.The crystallizedmate- (Li,K,Na,Ca,tr)s Be6P6O24(OH)a, basedon the observed minerals were independently density. rial was salvaged,and specimens sent for identification to the National Museum of Keywords:tiptopite, new mineral species,South Dakota' Natural Sciences,South Dakota Schoolof Mines and phosphate,pegmatite. Technologyand the SmithsonianInstitution. This unknowingly led to researchby independentgroups' SoNaMernE, which the authors discoveredprior to publication, La tiptopite, nouvelle espbcemin6rale, provient de la and which is reported in this synthesis.To date, 53 mine Tip Top, prds de Custer (Dakota du Sud); elle cris- phosphateminerals have beeu identified from the Tip tallise sur le b6ryl massifcomme min6ral secondairedans Top pegmatite. This includes eight.new species: une pegmatirce phosphate.Elle estassoci6e d: roscherite' jahnsite, robertsiteand segelerite(Moore &Ito 1974), fransoletite,montgomeryite s1 gnglishlls.La tiptopite se fransoletite (Peacor et al. 1983),tinsleyite (Dunn e/ prdsenteen agr6gatsfibroradi6s transparents, incolores et al, 1984),tiptopite (this study), and two other spe- prismes peuventatteindre 0.1 x lustrdsof les hexagonaux cies.A descriptionof someof theseassemblages was 0. 1 x 2.0 mm. Elle est fragile' d fracture irr6gulibre.Sa given by Dunn et al. (1983),For variety in secon- densitdmesur6e est de 2.65(2).C'est un min6ral optique- this locality is certainly one menruniaxe positif, <oi.sstlt;, e 1.559(1).Hexagonal, il dary phosphateminerals, in New appartient au groupp spatial PQ/m ou P63, avec 4 of significance,along with the Palermo mine I 1.655(5),c 4.692(2)A, et Z = l. Lesdix raiesde diffrac- Hampshire and the Hagendorf pegmatitesin Ger- 43 M THE CANADIAN MINERALOGIST many. One of the authors CIJC) is presentlystudying ciclesof clear, colorlessneedles that havea vitreous the mineralogyof the Tip Top pegmatitein detail. lustre (Fig. l). Individual crystalsare prismatic and The new mineral tiptopiteis namedfor the local- sometimeshave cavernous tubes at the ends(Frg. 2). ity. Both the new mineral and namehave been appro- Prismsare generallyI to 2.0 mm in length and less ved by the Commissionon New Mineralsand Mine- than 0.1 mm in width. ral Names,IMA. Cotype specimensof tiptopite are The mineral is brittle and has an unevenfracture in the collectionsof the National Museum of Natu- with no apparentcleavage. The hardnesscould not ral Sciences,Ottawa (NMNS #48833),the Smithso- be measuredowing to the small sizeof the crystals. nian Institution, Washington,D.C. (#149609),and It doesnot fluorescein ultraviolet radiation, and it the Museum of Geology, South Dakota School of is only slightly solublein 3090HCl. The determina- Mines, Rapid City (SDSM & T #81-5102). tion of density was difficult owing to the elongate OccunnBxcs habit of the crystals. Any turbulence in the heavy liquid causedthe crystalsto tumble erratically. The Tiptopite is found at the Tip Top mine locatedjust best experimentalset-up prpved to be a 15 mL rec- southwestof the centreof Sec.8, T3S, R4E, about tangular glasscell, viewedthrough the side with a 8.5 km southwestof Custer,South Dakota. Tiptop- stereomicroscopeand back illuminated with pola- ite wasdiscovered during mining operationsin 1981 rized light. Bromoform was diluted l:1 with butyl and 1982,in the recoveryofberyl from the outer- alcohol, which has approximatelythe samevapor intermediatezone. This zone consistsof large crystals pressureas bromoform. This minimized evaporation of microcline perthite, triphylite, quartz and mus- of the diluent and reducedthe "boiling" turbulence. covite, with minor amounts of beryl, albite, fluor- The experimentwas repeatedfour times using several apatite, elbaite and columbite-tantalite. Tiptopite crystalseach time. The resulting averagemeasured was abundant mine, at the but subsequentmining densityis 2.65Q)g/cm3. activity has removed most, if not all, of the area where it was found. Tiptopite occurspredominantly CRYSTALLOGRAPHY along fracture surfaces in beryl, occasionally in quartz, and rarely in microcline perthite. Morphology All observedcrystals of tiptopite have the same AppEARANcEaNn Puvsrcal PRopERTIES simple morphology: an elongatehexagonal prism Tiptopite occursas radial spraysand divergentfas- {100} and a basalpinacoid {001}. Optical data Optically, tiptopite is uniaxial positive (positive elongation)with indicesofrefraction co1.551(l) and e 1.559(l),measured in sodiumlight O 589 nm). X-ray-dffiaction data X-ray precessionphotographs show tiptopite to be hexagonal,with a choiceofpossible space-group P6/3/n1 or P63. The unit-cell dimensions were refined using X-ray powder-diffraction data obtained using a I 14.6-mm-diameter Debye-Scherrer camera with CuKcuradiation (Table l). The refined unit-cell parametersand volume are:.a 11.655(5),c 4.692(2) A and V 551.97(7.1)A3. The unit cell, spacegroup and generalconforma- tion of the formula are similar to those of cancrinite. For example,Grundy & Hassan(1982) showed that a carbonate-rich cancrinitp has cell parameters a 12.590(3)and c 5.117(l) A and spacegroup P6,. Thesecell parametersare larger than those of tiptop- ite by an amount consistentwith the differencesin radius of the tetrahedrally co-ordinated cations. Precessionphotographs of cancrinitewere directly comparedwith those of tiptopite, showing that there was similarity in the intensity values of equivalent Ftc. 1. Photomicrographof radial aggregatesof acicular reflectionsof eachphase. With this strong implica- tiptopite and white bals of englishite.Central sprayis tion of an isotypic relationship, three-dimensional 2.0 mm in diameter. intensitydata havebeen measured for tiptopite and TIPTOPITE, A NEW SPECIESFROM THE BLACK HILLS, SOUTH DAKOTA 45 Ftc. 2. Scanning-electron-microscopephotograph of tiptopite. 'I. an attempt is being made to determine the detailed TABLE X.RAYPOWDER-DIFFMCTION DATA crystal-structure. FORTIPTOPITE CrrsMrcar ColtposnroN dcal c dobs I hkl dcalc dobs 'f l0 5.83 5.79 1 241 1.767 1.767 2 Owing to the particular elementspresent, it was 020 5.05 5.08 2 042 L718 1.7t8 3 nece$saryto employ several analytical means to 011 4,2s 4.26 3 tsl I.691 1.692 3 120 3.815 3.808 4 232 1.648 1.647 1 determinethe chemicalcomposition of tiptopite. Ca, lll 3.654 3.652 4 142 1.606 1.606 4 K, Na, Al, Mn and P were determinedby wave- 021 3.440 3.441 3 341 1.564 'L1.564 I 030 3.364 3.364 5 013 I.546 543 '2 length-dispersion electron-microprobe analyses, 't0 lErO 1 121 2.960 2.966 251 .l.510I.528 'I using montgomeryite (Ca, Al, P), maridite (Na), 130 2.800 2.800 % 113 .51I ' hornblende(K) and manganite(Mn) 031 2.734 2,736 1 332 1.496 1.495 2 as standards. 040 2.523 2.525 9 023 1.494 An ARL-SEMQ microprobewas 'I 'I usedwith operat- ]3l 2.404 2.403 161 1,462 .459 6 ing conditions of 15 kV, samplecurrent 0.025 pA 002 2.346 2.348 7 '123440 1.457 230 2.316 2.3t5 1 1.447 'I1,447 3 (standardizedon brass) and a defocusedbeam to 012 2.285 2,283 ,2 152 I.434 .434 '2 minimize volatilization of the lighter elements.The 041 2.222 2,223 6 260 1.400 1.397 '2 112 2.176 2.175 2 223 I.378 'II.378 | data were correctedusing the MAGIC-4 computer 231 2.076 2.077 5 062 1.367 .367 '2 program.