Ameican Mineralogist, Volume 63, pages 704-708, 1978
Parnauiteand goudevite, two fromthe Majuba Hill Mine, "iir"r,flnffHffHjirffifls
Wrlr-reu S.Wrsr Departmentof GeologicalSciences, Uniuersity of California Santa Bsrbara, Calift rnia 93 I 06
Abstract
Parnauiteand goudeyitewere found with other secondarycopper minerals in the middle adit levelof the Majuba Hill Mine, PershingCounty, Nevada. Parnauiteoccurs as pale-blue fans and rosettesoflath-like crystalsup to I mm in length,as greenscales and crusts,and drusy surfacecoatings. A combinationof electronmicroprobe analysesand microanalysesfor Hro and Co, give the following composition:cuo 5g.10, AlzOs0.42,P2Or2.56,AsrOu 13.69, COr 0.7, SO, 6.33,HrO 17.7percent, sum 99.50.The empiricalcell contentsare CurrAlo.,(AsOa)r.os(por)0.4s(SO{)0.e1(COs)o.D(OH)ro.6.gHrO,with an idealformula of Cu'(Aso.)r(SolXoH)r0.7Hzo.The crystals are blades, flattened on {0101 and elongatedparallel to c. The mineral is orthorhombicwith a probablespace group of P2'22.Thecell dimensions are 4: 14.98(l),b: 14.223(8),and c = 6.018(8)4;Z:2,D (meas;=3.99. The strongestlines of the X-ray powerpattern (30 given) are 14.30(100)(010); r0.38(24Xlr0);7.14 (10X020); 6.a29)(120);4.52 (60Xl3q;a.00(2r)(230);2.84e (le)(0s0); 2.798(8Xl 50).The refractiveindices are d = 1.650,B : 1.7Q4,.y: 1.712, 2V, : 69",andno observabledispersion of the optic axes.The optic planeis parallelto {100},x = b, y : a, and Z: ciX palegreen,Yyellow-green,andz blue-green withZ> y > x.Theminerardissolves readilyin dilute HCI with the evolutionof CO, bubbles.The namehonors John L. Parnau.a mineral collectorof Sunnyvale,california, who was the first to find the mineral. Goudeyiteis theAl analogof agarditeand is thereforea newmember of themixite group. It occurs as yellow-greenhair-like crystals,encrusting fractures and as cross-fiberveinlets. Microprobeanalyses with separatedeterminations for HrO give the following composition: CaO 1.37,CuO 46.77,A1,Or 4.00, Y,Os 3.40, P,O6 4.55, AsrOu 27.85, HrO ll.0 percent,sum 98.94.This correspondsto Ca"rrCuusoAlo.??y.zs(AsOn)r{o(po4)0.ffi(OH)6.r?.2.95HrO and an idealformula cuuAl(Aso.)r(oH)6.3Hro. The crystalsare hexagonal prisms up to 0.5mm in lengthand 2 p.min diameter.The X-ray powderpattern was indexed by analogywith agardite, givingthe celldimensions a: 13.472(l)and c : 5.902(4)A;Z = 2, D (meas): 3.50.The strongestlines of the X-ray powderpattern (30 given)are 11.63(100)(100); a.al g3\(2lo); 3.53 (l5x2rt);3.367 (20)(220);3.23s (46)(310); 2.920 (50Xa00); 2.677 (42)(320);2.546 (40X410).The refractiveindices are"l : 1.704and e : 1.765;ois paleyellow-green and e is greenwith e )
Introduction describedby Smith and Gianella(1942), Trites and The Majuba Hill Mine (northernPershing County, Thurston (1958),and MacKenzieand Bookstrom Nevada)is locatedin a subvolcaniccomplex of rhyo- (1976).The mine producedonly 25,000tons of cop- litic porphyriesand brecciasintruded during mid- per ore and 350tons of tin ore but is widelyknown Tertiary time. The geologyof the deposithas been for the rich suiteof secondarycopper and iron arse- m$-0ax/78/0708-0704$02.00 tot WISE: PARNAUITE AND GOUDEYITE 705 nate minerals.A comprehensivestudy of thesesec- Parnauite ondary mineralsrevealed two new copper arsenate minerals. Physicalproperties and habit Theseminerals are named parnauite and goudeyite The habit of parnauitegreatly resembles that com- after John L. Parnau,a mineral collectorof Sunny- monly exhibitedby tyrolite. Where individual crys- vale,California, and HatfieldGoudey, a mininggeol- tals occur, they are lath-like in groupsforming fans ogist and mineralcollector of SanMateo, California. or rosettes(Fig. I ). Parnauitein thishabit is paleblue Over the past 40 years both men have made sub- and is closelyassociated with chrysocolla.Green to stantialbut unpublishedcontributions to the miner- blue-greenscales and crustsare more common' Sev- alogy of the Majuba Hill deposit.The nameswere eral specimenshave been found with yellow-green approvedby the Commissionon new Mineralsand parnauitein a radiatingstructure on a drusysurface. Mineral Names, IMA, prior to publication.The The lath-like crystalsare typically lessthan I mm namesare pronounced par-NO-ite and GOW-dee-ite. long, 0.5 mm wide, and only I to 5 pm thick. The Type materialof parnauite(a few hundredmilli- growths forming scalesand crusts have indistinct grams)and goudeyite(a few tensof milligrams)have crystalsbut yield the purestsamples, which were used beendeposited in the mineral collectionat the Uni- to provide material for the chemicalanalyses and versity of California, Santa Barbara (specimens densitydeterminations. 18090and #8091,respectively). Cotype material has The compactcrusts are estimatedto havea Mohs' beendeposited in the NationalMuseum of Natural hardnessnear 2, and a densityof 3.09(+0.04) gml History,Smithsonian Institution, Washington, D. C. cm3. as measuredwith a Berman balanceon frag- mentsof l0 mg in tolueneat 22"C. Opticallypar- nauiteis biaxialnegative with2V.: 60'(*5") and Occurrence no discernabledispersion. The refractiveindices are a The MajubaHill Mine exploiteda relativelysmall : 1.680,0 : 1.704,1: 1.712(each i0.003). The copper ore body on three adit levels,spaced about opticplane is parallelto {100},and X : b,Y : a, and 200 feet (60 m) apart in elevation.Most of the ore Z : c. In this respectparnauite can be distinguished was removed from various stopesmined from the from tyrolite, which is length-fastwhen the bladed middleadit (seeplate 9, Tritesand Thurston,1958). crystalsare lying on the latgeb face.Moreover,2Vo The largestof thesestopes is commonlyknown asthe (tyrolite): 36o.Parnauite is weaklypleochroic with Copper Stope and is labelledon Trites and Thurs- X palegreen, )'yellow-green, and Z blue-gteen;Z ) ton's plan and elevationdrawings of the workings. Y>X. Most of the primary ore minerals-chalcopyrite, arsenopyrite,pyrrhotite, pyrite, and cassiterite-orig- inated with three of the sevenintrusive pulsesand were concentratedalong severalfault zones(Mac- Kenzie and Bookstrom.1976). Oxidation occurred alongthese same fault zones, and secondaryminerals weredeposited in most fracturesbetween the surface andthe middle adit, a depthof about250 feet (75 m). The newminerals were collected from the workings of the middle adit. Parnauitewas collectedfrom the walls and ceiling of crosscut212 near the Copper Stope (see plate 9, Trites and Thurston, 1958). Goudeyitecame from a smallstope about 100feet (30 m) north of the entranceto the CopperStope. Com- mon secondaryminerals in and near the Copper Stopeare olivenite, clinoclase, cornwallite, strashimi- rite, scorodite, pharmacosiderite,arthurite, meta- zeunerite,chalcanthite, and chrysocolla.Less com- Fig. l. Scanningelectron photomicrograph of the bladedhabit mon minerals are spangolite,chalcophyllite, of parnauite.Length of bar is 250pm; thewidth of the bladesis less malachite,azurite, and brochantite. than5 rm. IIIISE: PARNAUITE AND GOUDEYITE
Crystallographyand X-ray dffiaction data Chemicalcomposition The cell dimensionswere determined from crystals Severalclusters or scalesfrom eachof the three in the lath-likehabit by meansof an h\l precession differenthabits were embeddedin epoxy,ground to photograph,a c-axisrotation photograph,and an exposethe centers,and coated with approximately fttO Weissenbergphotograph, allowing at leasttwo 200,{ of carbon. Analyseswere carried out on ten independentdeterminations of eachcell edge.The spots with an Anl electron microprobe, using an celldimensions from a least-squaresrefinement of the acceleratingvoltage of l5 kV for all elementsand a X-ray powderdiffraction pattern (Table I ), standard- samplecurrent of 8 nanoamps.The spot sizewas ized with annealedsynthetic CaF" (a : 5.4594),us- madeas largeas the sampleswould allow (up to 20 ingCuKa radiation (I : l.54l8A),are: a: 14.98(l), pm). Standardsinclude olivenite for Cu andAs, chal- b : 14.223(8),c : 6.018(8)A. cophyllite for Al and S, and apatite for P. Inter- The diffraction symmetryis mmm, indicating or- elementeffects were correctedwith a modified ver- thorhombic symmetry. Indexing the Weissenberg sion of the computerprogram EuploR 7 (Rucklidge photographsreveals no limitations in the hkl reflec- and Gasparrini,1969). tions, although all I odd reflectionsare very weak.In Water and CO, analyseswere obtained from a the ft00 reflections,h : 2n. The photographsdo not Hewlett-PackardC-H-N analyzer,using samples of 2 give clear evidenceof extinctionsin the h\l and \kl to 3 mg. Artinite was usedas a standard,and the sets.These relations, nevertheless, suggest the space reported valuesare probably accurateto within 5 group P222. percent.Thermal gravimetric analysisof the water The lath-likecrystals are elongatedparallel to c losson a 5 mg sampleshowed a steadyweight loss up and flattenedparallel to {010}. to 250oC.A sharploss occurred at 350oC.The early lossis interpretedto involvethe structuralwater, and Table l. X-ray powder diffraction data for parnauite the latterwas expulsion of the hydroxylwater. A summaryof the analysesis presentedin Table2. hkL I. carc ODS oDs Althoughphosphate is presentin all samplesof par- 010 14.) 100 nauite analyzed,it doesnot appearto be an essential 110 10.31 1n ?A 24 constituent,because all the arsenateminerals at Ma- 020 t 11 ?.r4 10 r20 6.42 6.42 I juba Hill, includingolivenite and clinoclase,contain 101 5.61 about20 percent phosphate. Sulfate with carbonateis 220 5.t6 5.76 7 030 4.741 +.73 2 Table2. Compositionof parnauite 3ro 4.7r) 130 4.52 4.52 60 (1) (2\ (3) ()+) 230 4, 00 4.00 27 0l+0 ).56 6 cuo 140 3.46 3.46 6 58.10 58.69 58.95 57.55 330 3.44 3,44 7 [eO3 0. )+2 l-.f I 0.1+5 240 3,21 3,27 4 510 2.93 2.93 + PzO, 2.56 2.39 2.58 As205 73.69 rl+. . 06 2.90 2.90 I 50 f3 rB. 5r )40 'to 050 2.u5 2.8+9 so3 6.33 5.31 5.\5 6.\5 750 2.795 2.798 B 520 2.?6t t a<, co2 0.7 250 z.otY t AAa HzO t7 .7 t7 ?o 302 2.577 2.57? 7 3t2 z. tto 2.537 6 Total 99.50 82.00 81.50 100.00 2.532 2.529 7 402 2.3A.51 160 z.*tI 2.Yr+ 2 (1) (2) 4L2 2.3L4 2 ].75 1 cpeen c?usts and scales, bLue-green bLades 450 in z,osettes, (3) yeLLou-green dzwsy surfaee eoating, ?42 z.ze+ (4) ideaL cun(Asol (oH) |}zfl r(sol fi'7H20. )60 2.I4r 2.!+I 2 640 2.d13 2.d+ I ErnpirieaL ceLL eontents : 460 2.003 2.01 2 hs.z#1 2?O L.96L 1.96 1 .n(Ason)r.nt(P)l .$(s0l .s4(c0l.Is(ov) z.so phis 8 d.efinable peaks, but with lntenslties less than 1 to cI = 1.j} 6.81 820. I4IISE: PARNAUITE AND GOUDEYITE '707
interpretedto be a separate,but essential,constitu- Table3. Comparisonof theproperties of themixite group ent-very similarto tyrolite.The completelack of Ca in parnauiteis the most significantdifference in com- Goud.eylte Agarrllte lli:rite parisonwith tyrolite. 7.7U r,707 L.?43 t 7.765 L.?82 1 .830 Goudeyite o (sm/cn3) J.OU "qn Physicalproperties and habit ' (r) 73.t+7 13.g+ Goudeyite occurs as hair-like crystalsin tufted (a) " ),vo t.>o groups,encrusting fracture coatings, and cross-fiber Color ye11ow- blue- enerald.-green veinlets.Individual crystalsare simple hexagonal Sreen green blue-green prisms,elongated parallel to the c axis. Scanning electronmicrographs (Fig. 2) show the averagecrys- tal diameterof about2 pm.Thelengths do not exceed ite and mixite are identical, and mixite has the space 0.5 mm. Goudeyiteis yellow-greenwhere compact group symmetry P6g/m or P6r, goudeyite appears to and lighter in dispersedtufts. The compactmasses have the same symmetry. have a hardnessbetween 3 and 4, and a densityof Chemical composition 3.50 (+0.03) gmlcm3 as measuredwith a Berman balanceon fragmentsof 8 mg in tolueneat 22"C. Goudeyite was analyzed by the same electron mi- Goudeyiteis uniaxialpositive with co: 1.704and e croprobe methods described earlier but with the fol- : 1.765(each *0.002) in white light; dichroic,c,r is lowing standards: conichalcite for Ca, olivenite for paleyellow-green and e is greenwith e ) co.Table 3 is Cu and As, apatite for P, gadolinite for Y, and K- a comparisonof the propertiesof goudeyitewith feldspar for Al. HzO was determinedby weight loss mixiteand agardite. Table 4. X-ray powder diffraction data for goudeyite Crystallographyand X-ray diffraction data i Singlecrystals are far too small for single-crystal ca-Lc oos oDs X-ray diffraction study. However,the X-ray powder 100 rr.67 r7.63 100 2t0 t+.+I 4.41 43 diffractionpattern is easilyindexed by analogywith 20I 4.r5 4.15 3 agardite(Dietrich et al.,1969).A least-squaresrefine- 300 3.89 3.89 7 ?(? ?<" mentof thecell dimensions yields a : 13.472(l)and c 217 15 : 5.902(4)A.See Table 4 for the indexedpowder 220 ? ?AA ).36? 20 370 ) .2)o ).235 t+6 pattern.Since the X-ray powderpatterns of goudey- 400 2.9r7 2,920 50 all 2.8)7 2.u0 5 )zv z.o /o 2.6?? +2 401 2.614 z.618 1 +10 2.546 2.96 46 212 2,452 z.t+J+9 r2 420 2 2a< 2.205 4 2.7?o 1 510 2.095 2,096 421 z.vo) 2.068 ? 322 t.982 1.98 1 6oo L.7q) r.945 7 4)O 1.918 1,920 6 520 1 .868 I.B? 1 l+31 7.824 1 At< 2 L.7BT r.782 422 1 aAA 4 512 r,709 1.,?09 a 4l+0 1 .681+ L5g+ 4 530 7.667 1 AAn 4 602 1.624 r.oz) 1 .5011 1.505 4 122 L.578 1 .5Bo 1 plus 15 definabLe peaks but with Fig.2. Scanning electron photomicrograph of goudeyite. Length intensities less than 1 to aI = 1.2 of baris l0 rm. 708 IIISE: PARNAUITE AND GOUDEYITE
Table 5. Compositionof goudeyite arsenate,/phosphateratio is consistently4/l in the
(1) (2) samplesanalysed. Dietrich et al. (1969) showed in a study of 3l Ca0 1.37 samplesfrom eleven localities in Europe and the CuO \6.7"1 \8.55 United Statesthat all known "chlorotile" specimens Ar_^0^ 4.00 5.20 wereeither mixite or agardite.Chemical tests showed 3.Lo either the presenceof Bi or rare-earthelements with DA Y. Walenta(1970) described various members of the As^0- 27.85 35.11 chlorotile-mixitegroup from the Black Forest and H^0 11.0 11.01 the Erzgebirgeand found samplescontaining rare earthsas well as Bi. Only one mixite samplecon- Total 98.9\ r-00.00 tainedsignificant amounts of Al. None of his samples had an a dimensionless than the 13.55,{value of agardite(Table 3). (1) Ave"age of fiue eleetyon micz,opnobeanalysea H20 by ueight Loes in heating a single 5 ngn sanple t6 600"c. References Dietrich,J.-E., M. Orliacand F. Permingeat(1969) L.'agardite, une (2) IdeaL CUUAL(AeOl r(oH) u.3Hr0. nouvelleespdce min6rale, et deprobl0me du chlorotile..Bnl/.Soc. hnpirieal eeLl contente: fr. Mineral. Cristallogr., 92, 42U434. MacKenzie,W. B. and A. A. Bookstrom(1976) Geology of the tu Asl 2. s5H s. BoCo, zaAL . r rI . rn( I z. eo(Po | . oa( 0H ) 6. n' z0 Majuba Hill area,Pershing County, Nevada. Neuada Bur. Mines Geol. Bull. 86. Ruckfidge,J. and E. L. Gasparrini(1969) EMPADR VII, a Com- puter Program for Processing Electron Microprobe Analytical upon heatinga 5 mg sampleto 600oC.An averageof Data. Department of Geology, University of Toronto. five analysesare given in Table 5 along with the Smith,W. C. and V. P. Gianella(1942)Tin deposit at Majuba Hill, Pershing empirical County,Nevada. U. S. Geol.Suru. Bull.,931-C,39-55. cell contents. Trites,A. F. and R. H. Thurston(1958) Geology of MajubaHill, It is clearfrom the data in Tables3, 4, and 5 that PershingCounty, Nevada. U. S. Geol. Suru.Bull., 1046-1,183- goudeyite is a new member of the mixite gtoup, 203. which appears to have the general formula Walenta,K. (1970)Mineralien der Chlorotil-Mixitgruppemit sel- CuuR(AsOo)r(OH)..3H2O,where R can be Al, Y tenenErden von Fundortenim Schwarzwald.Chemie der Erde, 29. 36-47. (and rareearths), and Bi. The extentto whichphos- phate can substitutefor arsenatein this seriesis not Manuscript receiued,February 22, 1978;accepted revealedby the Majuba Hill samples,because the for publication,March 30, 1978.