AmericanMineralogist, Volume 70, pages 419422, 1985

Kambaldait+a new hvdrated Ni-Na carbonatemineral from Kamnatda,

EnNesr H. Nrcxel exo Bnucp W. RosrlrsoN Division of Mineralosy, CSIRO Private Bag, P. O., Wembley, Western Australia, 6014

Abstract

Kambaldaitehas the ideal compositionNa2Ni8(CO3)6(OH)6'6H2O. It is hexagonal, space group P63, with a : l0.34OA and c : 6.0974; Z : l. Strongest X-ray powder difraction lines are: 9.03(l0xl0T0), 4.490(9)(2020),3.613(4)QA.l), 2.681(4x3031), 2.584(4)Qfn), 2.519(4)(2@2)and 2.263(4)(2132).The mineral occurs as needles and prismatic crystals elongatedalong c, as well as cryptocrystalline masses.Uniaxial positive, with

Introduction Keele and Nickel (1974). The primary sulfides, which occur as assemblagesof -pyrrhotite-pyrite The Kambalda nickel sulfide deposits, 56 km south of and pentlandite--pyrite, have been altered to Kalgoorlie in Western Australia, have been the source of supergeneassemblages consisting largely of and a number of secondary nickel minerals, including ga- pyrite, which have decomposedon further oxidation to a sp€ite, takovite, reevesite, pecoraite, morenosite, retger- goethitic residue in which the secondary nickel minerals site, nickelhexahydrite, nickelblodite and hydrohones- have been deposited. site. The last two were discovered as new minerals at The samplesin which the kambaldaite was found are Kambalda (Nickel and Bridge, 1977; Nickel and Wild- from a depth of about 20 meters, and consist largely of man, 1981). with some reevesite and residual pyrite. The This paper describes another new mineral from the kambaldaite, together with gasp6iteand some aragonite, locality. It was initially observed by Mr. David Vaughan occurs on fracture surfacesin the goethite. The kambal- of Perth, Western Australia, in material collected by Mr. daite occurs in a variety of types: massive, crystalline, R. Harrison of Kambalda, from the No. I ventilation nodular and chalky. shaft of the Otter Shoot, one of the Kambalda nickel The massive kambaldaite occurs as cryptocrystalline mines. Mr. Vaughan brought samples containing the veins, layers and concretionary growths up to about 2 mm mineral to the laboratories of the Division of Mineralogy, thick, commonly intergrown with gasp€ite. Although cslRo, for identification, where it was determined to be a both mineralsare green, they have different shadesofthis new mineral. color, gasp6ite having an olive-green cast compared to The mineral was namedkambaldaite in referenceto the the more emerald-greenshade of the kambaldaite. locality of its discovery, and both mineral and name have The crystalline kambaldaiteoccurs as encrustationson beenapproved by the I.M.A. Commissionon New Min- the more massive kambaldaite and on gasp6ite. The erals and Mineral Names. The holotype specimen is encrustationsare bright grass green to emerald-greenin retained in the mineral collection of the Division of color, and generallyconsist of tiny hexagonalprisms (Fig' Mineralogy, csIno, in Perth, Western Australia; cotype 1a).Most of the prisms are terminatedby basalpinacoids, specimenshave been lodged with the Government Chem- and a few are zoned, with a clear core and a translucent ical Laboratories of Western Australia, the Australian marginal zone; when viewed end-on, such crystals have a Museum in Sydney, the British Museum of Natural striking "fish-eye" appearance.A few crystals are termi- History in London, and the Smithsonian Institution in nated by second-orderpyramids (Fig. lb), together with Washington,D.C. small pinacoidal faces. These faces commonly contain fine pits, which may represent the openings of tiny Occurrence and morphological description solution channelsalong the c axis. The mineralogy of the primary and supergenesulfide The nodular kambaldaite occurs as partial spheres assemblagesin the Otter Shoot has been described by about I mm in diameter (Fig. lc). Some of the nodules, 0003-{04xl8s/0304-04 I 9$02.00 419 420 NICKEL AND ROBINSON: KAMBALDAITE

Fig. l. (a) SEM micrograph of prismatic crystals; (b) SEM micrograph of a kambaldaite crystal with first order prism faces, second-orderpyramid faces, and a pitted basal pinacoid; (c) Optical photographshowing sub-sphericalnodules ofkambaldaite. The white mineral is aragonite;(d) SEM micrograph ofa broken sub-sphericalnodule, showingthat the sphericalsurface is composedof basal pinacoids of hexagonalprismatic crytals. such as the ones shown in Figure lc are very glossy and and using an energy-dispersiveprocedure developed by have a rich emerald-greencolor. When these spheresare N. G. Ware (Ware, 1981).Carbon and hydrogen were broken, they are seen to consist of radiating hexagonal determined on a handpicked sample of massive kambal- prisms, the pinacoidal faces of which comprisethe spheri- daite by R. D. MacDonald of the Australian Microanalyti- cal surfacesofthe nodules(Fig. 1d).Other nodules,paler cal Service. The results of the analyses, converted to green in color, consist of fine radiating needles about I oxides, are shown in Table l. The ideal compositionof pm or less in diameter; when these nodules are broken kambaldaite,Na2Nfu(CO3)6(OH)o . 6H2O, is also given in open, they are pale green, with a silky luster. Table l. The chalky kambaldaiteconsists of pale green pulveru- The empirical formula for kambaldaite obtained from lent material which, at high magnifications under the the analysis, using the measured density and unit-cell scanningelectron microscope (SEM), is seento consistof parameters(vide intra), and apportioning the H between massesof very fine acicular crytals up to ca. l0 pm long OH- and H2O to preserve charge balance, is Na1s5 and up to I pm in diameter. (Ni7.s1Mgs:o)>:a 17 (C6.s6AlsesSi6.saSs.s3)1:t.otOzo D (OH)3e75.67H2O. Ignoring the minor constituents,com- Composition parison with the ideal formula shows that Na and H2O are Crystals of kambaldaite were embedded in plastic lower, and C is higher. The low H2O and high C values resin, sectioned, polished, and then analyzed with an can be attributed to the presenceof some gasp€itein the MAC electron microprobe analyzer operated at 15 kV, sample analyzed for H and C, since an X-ray powder NICKEL AND ROBINSON: KAMBALDAITE 421

Table 1. Empirical and ideal composition of kambaldaite length-slow.Kambaldaite is dichroic in transmitted light, with E : emerald green, and O : light green. KaDbaldarte NazNiB(co3)6(oH)6 6Hzo The mineral is not readilv solublein cold 1:1 HCI or gtt ttt l: I HNO3. La2O 3.O 5.7I Discussion Nro 52.9 55.04 A search of the mineralogical literature has failed to l{9O r.3 reveal any minerals with composition or structure similar coz 24.32 to those of kambaldaite, and no mineral analogueshave

Al2O3 o.4 been discovered.Neither have close relatives been found in tabulations of inorganic substances.It therefore ap- SrO2 o.2 pearsthat kambaldaiteis a unique mineral specieswith no So3 o.3 known relatives. Hzo I2,5 14, 93 The mineral occurs near the base of the oxide zone in weathering profile, where the activity of 90,1 roo. oo the supergene nickel speciesin solution is particularly high due to the dissolution of violarite. Carbonate and sodium activities must also have been high for kambaldaite to form. Carbonates are common in the wallrock and ore, and diffraction pattern of the analyzed concentrate contains their dissolution should create a high level of carbonate the strongestgaspeite lines superimposedon the kambal- activity. Although there are no appreciable amounts of daite pattern. The low empirical Na content may be due to the loss of some of the Na under the electron beam during electron microprobe analysis, a phenomenonthat powderdiffraction pattern of kambaldaite has been reported by Autefage (1980),among others, and Table 2. X-ray severalmicroprobe experimentsdone on the kambaldaite d support this suggestion.The apparent loss of Na is not I hki obs . surprising, since crystal-structure analysis (Engelhardt et lo IoJ.o 9, 03 8,955 al., 1985)has shown that the sodiumions, coordinatedby 2 LoLL 5, 053 5. o+o in relatively large c-axis 9 2020 4.490 4.4?7 water molecules, are located 4 202L 3.613 3.609 channels, and can therefore be expected to be relatively I OOO2 3.O49 3.O48 2 3030 2.98s 2.945 mobile. 4 3031. 2.64L 2.64! + 2240 2.58+ 2.585 X-ray crystallography and physical properties 4 2022 2-5L9 2.520 2 L340 2.445 2.4e+ Single-crystalX-ray diffraction analysisof kambaldaite r 2241 2 3€O 2.380 I 3r4r 2.300 2,300 has shown that the mineral is hexagonal, with space + 2L32 2.263 2.265 group P63. The unit-cell parameters,obtained during the l 4040 2.2?? 2.239 I 4041 2.096 2.!OI course of crystal-structure analysis (Enqelhardt et al., r 3250 2.O53 2.O54 1985)are a : 10.340(3)and c : 6.097(2)4.The crystal- 1 2242 r.910 r.972 'l:25:.- J4r5ol ''"". ^-^ tr.es4 structure analysis showed that the structural formula is 1 lt.s+z Na2Ni6(CO3)6(OH)o'6H2O, with Z : 1. The powder 2 3742 7.92+ L.925 I tl23 1..ssg l. 89r difraction pattern, obtained with a Guinier camera, using f 4f5l r.85? I . 86r thoria as internal standard, is given in Table 2. 3 4042 1,802 I.804 1 2133 L.'t19 7.?42 Kambaldaite has a pale green streak. Its density, t !252 l. .701 1.704 measured on single crytals by the sink-float method in 2 4260 1,690 r.692 t 51.6I r.5s3 J. 555 g/cm3. density of ideal 404-31 ( r. sos heavy liquids, is 3.18 Calculated 'lrol*/. { '''"". -^^ NazNis(CO3)e(OH)o' 6HzO is 3.193.the densitycalculat- lr.sor 2 6060 l. +89 r .492 ed from the empirical composition, according to the 3 4262 I.4?8 L+80 Gladstone-Dalerelationship, and using Mandarino's val- 2 7L24 r.459 I. il62 '\zoz+l^ {32t31 ''"*'- --. 1f.445 ues for specific refractive energies of the oxide compo- \r.++a nents (Mandarino, 1976)is 3.183.Hardness is approxi- 7 5062 t 338 1.340 I 617l- r . 330 L. 333 mately 3 on Mohs' scale. Cleavageis not discernible. The most common crystal form is a hexagonal prism with Pdd€t data obtaaned uelng 80 m Guinaer caGra sith {10T0}and {0001}terminations; less common are second- CuKc radiatlon' Tttoz order pyramids,probably {l l2l}. rnternal standdd' Kambaldaite is uniaxial positive, with refractive indi- *a=ro.3aoi, c-6.oez^f ceso : 1.65and e: 1.69;prismatic crytals are therefore 422 NICKEL AND ROBINSON: KAMBALDAITE sodium minerals in the primary rock, the groundwater in structure of kambaldaite,NazNia(COr)e(OH)o' 6H2O. Ameri- the regionis very saline,values of up to 5.9%Nahaving can Mineralogist,7 0, 423427. been reported (Nickel et aI., 1974). This high sodium Keele, R. A. and Nickel, E. H. (1974)The geology of a primary content is probably due to seepagefrom salt lakes in the millerite-bearing sulfide assemblageand supergenealteration at the Otter Shoot, Kambalda, Western Australia. Economic vicinity. It therefore seemslikely that kambaldaite owes Geology, 69, ll02-lll7 . its origin to an unusual combination of elements in the Mandarino, J. A. (1976)the Gladstone-Da.le groundwater. relationship-Part Significantly, the only other secondaryNa- l: Derivation of new constants. Canadian Mineralogist, l+, Ni mineral found to date, namely nickelblodite (Nickel 498-502. and Bridge, 1977)was also found at Kambalda. Nickel, E. H. and Bridge, P. I. (1977) Nickelbki'dite, Na2Ni (SO+)z' 4H2O,a new mineral from Western Australia. Miner- Acknowledgments alogical Magazine, 41, 3741. The samplesfor this study were provided by Mr. David Nickel, E. H., Ross, J. R., and Thornber, M. R. (1974)The Vaughanof Perth,and we appreciatehis cooperationin making supergenealteration of pyrrhotite-pentlandite ore at Kam- all his materialavailable to us. Helpful commentstoward the balda, Western Australia. Economic Geology, 69, 93-107. preparationof the data for publicationwere madeby Dr. A. Nickel, E. H. and Wildman,J. E. (1981)Hydrohonessite-a new Kato,past chairman of theI.M.A. Commissionon New Minerals hydrated Ni-Fe hydroxy-sulphate mineral; its relationship to andMineral Names. The author's colleague, Dr. D. R. Hudson, honessite,carrboydite, and minerals of the pyroaurite group. madehelpful comments on the prepartionof the manuscript. Mineralogical Magazine, 44, 333-j37. Ware, N. G. (1981)Computer programsand calibration with the PIBStechnique for quantitative electron probe analysisusing a References lithium-drifted silicon detector. Computers and Geosciences, Autefage,F. (1980)Variations de la teneuren sodiumet en 7. 167-184. potassiumdans les min€rauxau cours de leur analysed la microsonde6lectronique. Bulletin de Mindralogie,103, 48-53. Manuscript received, March 28, 1983; Engelhardt,L. M., Hall,S. R., andWhite, A. H. (1985)Crystal accepted for publication, J uly 24, l9M.