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, 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. Becauseof the significantcontent of light 212 1.994 1.998 3 261 I.34I i??o , elements,possible variation in 330 1.942 I.943 4 170 I.337 alkaline earths and 051 1.854 I.851 252 1.33r lack of any suitablephases to use for comparison, '1,827 , llln ? 222 1,827 2'I 043 1.329 a secondmicroprobe analysis was carried out using 132 1,798 1.800 233 1 .296 1.?97 3 different standards;this yielded virtually identical 'l Plus additi onal weak I ines : I .288, .274, 1.260 ' 1.437 , results.Except for trace amountsof Fe, Mg, Si and 1.228,1.219,1.209,1.193, 1.184, 1.172 and 1.162 A. F, which werenoted in both setsof analyses,no other element with atomic number greater than nine was Curoradiation, cell dinnnsJonsa I1.655(5)' c 4.692(2)A. detected. Beryllium and lithium were analyzed by atomic- 9.9, BeO 15.1,CaO 4.3, MnO 0.2, Al2O30.3, P2O5 absorption spectrophotometry,and confirmed by ion 55.1, H2O 3.4, sum 98.9 weight 70. Basedon the probe. Water was determinedby TGA with mass observeddensity of 2.65 g/cm3, the empirical for- spectrographicanalysis, and was evolvedbetween mula is (Li2.5sKr.6tNa1.75Cas.6sMns.oz)rz.oo(Bes.rt presence 550-900'C,with a peakat 788'C. The of P0.57A10.05)E6.00P6.00O8.j2[(OH)r.rr(POrsj5Jrz.t2 ot, minor CO, and SOr was also noted. ideally, (Li,K,Na,Ca, n )6Be6P6O2a(OH)0. The following is a compositeof the resultsof the The ideal formula for tiptopite is presentedin a aforementionedanalyses: Li2O 4.5, Na2O6.1, K2O format consistentwith that of the cancrinitegroup, 46 THE CANADIAN MINERALOGIST .46- sAl 65 i 6024 [ (S O 4) ( C O 3 ) C12 (O H ) ]2_ c. nH zO. tite form crusts on which montgomeryite and later Assumingthat Be is tetrahedrallyco-ordinated, the phosphatesare sometimesdeposiled; montgomeryrte ratio (Be+ P):(O + OII) requiresthat all or nearly all crystals also form directly on beryl along fracture verticesof tetrahedrabe sharedbetween Be and P. surfaces.Subsequently, tiptopite beganlo form, and Only if the OH is co-ordinatedto Be can the struc- the two mineralsare commonlyintergrown. During ture be other than a framework structure,as consis- and after the depositionof montgomeryiteand tip- tent with the analogywith cancrinite. However, there topite, eosphorite-childrenitecrystals formed, fol- are two significantproblems with the empiricalfor- lowed by spherulesof hurlbutite. Toward the end mula that concerntetrahedrally co-ordinated cations: of hurlbutite crystallization,spherulitic aggregates (l) the numberof Be atoms(5.38) is significantlyless of englishite,a moderatelyabundant mineral here than the rank of the availableequipoint (6). As the (Dunn el al. 1984), began to form; these are com- analysisalso has an excessof P, someof this P has monly impaled on acicular tiptopite crystals. beenassigned to the Be site, along with Al, to accom- Roscheriteformed contemporaneouslywith (and is modate the requirementsof the equipoint rank. sometimespartly coveredby) englishite.Whiteite, However, if the structure is isostructuralwith that wherepresent, is then formed. Platesand parallel- of cancrinite,this requiresthat somebridging oxy- stackedaggregates of fairfieldite weregenerally the gen atoms be sharedbetween two P ions. This is last to form, and whitlockite, where present, unreasonable.A secondexplanation for the defi- depositedas a dusting on the other minerals. ciency in Be may lie simply in analytical error. In either case,it is clear that the formula has six, or AcrNowI-spcsl,IsN'rs (2) nearly six, Be atoms. There is an excessof 0,92 The authorsthank P. Roederand D. Kempsonfor P atomsabove the 6 requiredby the availableequi- use of the University microprobe. J.-L. point. Queen's Part of this excesswas assignedto the Be site Bouvier at the GeologicalSurvey of Canadacarried and part (0.35) phosphate as a radical to the colum- out the AA analysis for beryllium and lithium, and (assuming nar voids a cancriniteJikestructure) con- R. Ramik at the Royal Ontario Museumperformed taining OH. This radical could occupy a crystal- the TGA analysisfor water. We also thank J. Jam- structuresite in much the sameway as sulfatein the bor at CANMET for his helpful suggestionswith the cancrinitestructure. There are numerousother pos- density determination, and H. Ehrle, who generously sibilities for rearrangingthe formula; one of the most provided sufficient material to enable characteriza' obvious is to fix the number of tetrahedrally co- tion of this mineral. ordinated cations (Be + Al + P) at 12 atoms. This, gives although sound in terms of crystal chemistry, REFERENCES a low calculateddensity of 2.58 g/cm3, compared to the observeddensity of 2.65 g/cm3.The problem DuNN, P.J., Ronenrs, W.L., Caurnslr, T.J. & of the formula will not be resolveduntil the crvstal LsevsNs, P.B. (1983): Red montgomeryite and structure is known. associatedminerals from the Tip Top pegmatite with notes on kingsmountite and calcioferrite, Mineral, Record 14, 195-198. PARAGENESIS The paragenesisof tiptopite is complex because Rousr, R.C., CaMpBsr-r,T.J. & Ronnnrs, W.L. (1984): Tinsleyite, the aluminum analogue of it occursin two similar, but distinct phosphateassem- leucophosphite, from the Tip Top pegmatite in blages.The first phosphateparagenesis, discussed South Dakota. Amer. Mineral. 69,374-376. in detail by Peacoret ol. (1983),is characterizedby whitlockite, which is a dominant early phase,red and GnuNnv, H.D. & Hessar.r,I. (1982): The crystal struc- yellow montgomeryite, tiptopite, englishite,hurlbut- ture of a carbonate-rich cancrinite. Can. Mineral. ite, red to orangeroscherite, whiteite, robertsiteor 20. 239-251. robertsite-mitridatite, fairfieldite and fransoletite. The secondphosphate suite, discussedbelow, con- Moonr, P.B. & Iro, J. (1974): I. Jahnsite,segelerite phosphate sistsof mitridatite, light brown to colorlessmont- and robertsite, three new transition metal species. II. Redefinition of overite, an isotype of gomeryite,tiptopite, eosphorite-childrenite,hurlbut- segelerite. III. Isotypy of robertsite, mitridatite, and ite, englishite,dark olive-greenroscherite, whiteite, arseniosiderite. Amer. Mineral. 59. 48-59. fairfieldite, whitlockite and another new mineral. An Cavrnnrr, obviousdifference is the overall color of the assem- Psacon,D.R., Dur.IN,P.J., Roannrs,W.L., T.J. & Nrwnunv, D. (1983):Fransoletite, a new cal- blages, as exemplified by roscherite and mont- cium beryllium phosphate from the Tip Top peg- gomeryite.Another differenceis that the secondsuite matite, Custer, South Dakota. Bull. Mindral. 706, containsmitridatite and eosphorite-childrenite,lacks 499-503. fransoletite, and does not have whitlockite as a dominant early phase. Received December 18, 1983, revised manuscript Lamellar aggregatesof dark red-brown mitrida- accepted April 4, 1984.