Eur. J. Mineral. 1993, 5, 679-683

Kamphaugite-(Y), a new hydrous Ca-(Y,REE)-carbonate mineral

GUNNAR RAADE and KJARTAN BRAS TAD

Mineralogisk-Geologisk Museum, Universitetet i Oslo, Sars' gate 1, N-0562 Oslo 5, Norway

Abstract: Kamphaugite-(Y)occurs as white to colourless platy crystals « 1mm across) in cavities of a magnetite-helvite skarn deposit at Hortekollen, Oslo region, Norway. It has been previously reported in the literature with insufficient data from the USSR, South Africa and Canada. The chemical composition is Ca2(Y,REEh(C03MOH)z.3H20. It is tetragonal, P41212, a=7.434(1), c=21.793(3)A; 2=4. The strongest reflections of the powder pattern for FeKul are [d in A, (lobs),(hkl)]: 6.140 (100)(102), 4.381 (80)(104),3.516 (60) (202), 2.831 (50) (214) and 2.631 (90) (220). The mineral from Hortekollen is anomalously biaxial with 2V(-) lY; u = 1.627, ~""y= 1.663 (:to.002). The density is 3.19:t 0.05 g/cm3 (meas.) and 3.24 g/cm3 (calc.). Mohs' ""hardness is about 2-3. Comparison is made with related REE-bearing carbonate minerals.

Key-words: new mineral, kamphaugite-(Y), tengerite, Ca-Y-REE-carbonate, Norway.

Introduction who supplied us with the first specimens for in- vestigation. Two other collectors, Hans Vidar The Ca-Y-carbonate mineral described in the pres- Ellingsen and Hermann Fylling, were also in- ent study has already been reported in the litera- volved in this new mineral find at the Hortekollen ture from three different localities, but with in- locality. The mineral and its name were approved sufficient data for a complete characterization. It by the Commission on New Minerals and Mineral was first described and identified as 'tengerite' by Names of the I.M.A. Type material is preserved Stepanov (1961) from a locality in Kazakhstan, in the Mineralogical-Geological Museum, Univer- USSR. Mineev (1974) used the term 'calcio- sity of Oslo, under catalogue no. 14769. tengerite' for the same mineral. Its X-ray powder pattern is similar to that of an unnamed Ca-Y-car- Previous work bonate from Transvaal, South Africa (Verwoerd, 1963). The third locality is in the Evans-Lou peg- The mineral described by Stepanov (1961) occurs matite, Quebec, Canada (Hogarth, 1972). as a secondary replacement product after gagari- Three Norwegian occurrences of the mineral nite, NaCaY(F,CI)6' in metasomatically altered are known. It was initially found as a fine-grained alkali granites from the Kazakh SSR. X-ray spec- alteration product of kuliokite-(Y) from the Hoy- trometric analyses of three samples show Ca, Y, dalen granite pegmatite, Tordal (Raade et aI., Yb as the main elements and variable contents of 1993). The discovery of considerably better crys- the REE, but with the Y group predominating. Re- tallized material in the Hortekollen deposit fractive indices are 1.620 and 1.642 for a white enabled us to describe this mineral as a new spe- sample and 1.611 and 1.636 for a yellow sample. cies. The third locality, the Tangen pegmatite The density is given as 2.85 gl cm3. The X-ray quarry near Kragero, was found by Ole T. Ljostad powder pattern was tentatively indexed on a tet- during the revision of this paper. Here the mineral ragonal cell with a=8.375, c=8.72A. DTA occurs as well-crystallized rosettes along cracks curves of two samples show endothermal peaks in quartz and feldspar. , at 130-200, 490-500, 580 and 710-760 "C. The mineral is named kamphaugite-(Y) after The South African mineral was discovered in Erling Kamphaug (1931-), a mineral collector a quartz-barite vein within the carbonatized

0935-1221/93/0005-0679 $ 1.25 1993 E. Schweizerbart'sche Verlagsbuchhandlung. 0-70176 Stuttgart "' 680 G. Raade & K. Brastad

Goudini volcano (Verwoerd, 1963). It occurs as divergent or rose-like aggregates, sometimes less than 1mm white spheroids on ferruginous growing to small spherules. It is moderately abun- opal, and effervesces in dilute acids. Optical emis- dant and, due to its thin-platy habit, the total sion spectrograms show Ca and Y as the main amount of material at hand may amount to only constituents with minor Yb, Er, Dy and Gd. One a few mg. It is white to colourless; small spherules of the refractive indices is 1.64 and the birefrin- may be weakly yellow to brown. The streak is gence is approximately 0.02. An unindexed white. The mineral is transparent and has a vit- powder pattern is tabulated which closely re- reous lustre. No fluorescence in ultra-violet light sembles that of the Kazakh mineral. was detected. Cleavage or parting were not ob- Hogarth (1972) has reported an unknown served. It is brittle with an uneven fracture. The mineral, designated UN-21, as white crusts on Mohs' hardness is about 2-3. Density was loose fragments in the pit of the Evans-Lou peg- measured as 3.19:t0.05 g/cm3 using heavy matite. It was noted to have a similar X-ray pat- liquids. Kamphaugite-(Y) from Hertekollen is tern to the 'tengerite' of Stepanov (1961) and the anomalously biaxial with 2V(-)"" 15°. The refrac- unidentified carbonate of Verwoerd (1963), but tive indices were measured in white light by the with the 2.73 A reflection greatly strengthened. immersion method (:to.002): a= 1.627, 13""Y= No other data have been published on this min- 1.663. Axial dispersion was not observed. The eral. acute bisectrix is perpendicular to the plates, i.e. X=c. Type locality X-ray crystallography With the present description of the new mineral, the Hertekollen occurrence at Lier, Buskerud, Single-crystal diffractometry shows the mineral to Norway, becomes the type locality of kamp- be tetragonal with possible space groups P412j2 haugite-(Y). It is a contact-metasomatic skarn or P432j2. The crystal structure was solved in deposit in the Oslo region, mined in the last cen- space group P4j2j2 to R=0.067 (Remming et aI., tury on a small scale for magnetite and described 1993). The cell parameters are a=7.434(1), c= in some detail by Goldschmidt (1911). Minerali- 21.793(3) A, v= 1204.4(3)A3. zation occurs at the contact between an isolated Observed and calculated X-ray powder pat- raft of Silurian sediments, about 20 m long, and terns are given in Table 1. The experimental pat- a Permian biotite granite, the Finnemarka granite. tern was obtained with a 9 cm Debye-Scherrer The principal skarn minerals are helvite, grossu- camera using FeKaj radiation. No internal stand- lar, fluorite, quartz and alkali feldspar, with sub- ard was used, but the data have been corrected to ordinate biotite, pyroxene, amphibole, wollas- conform with the results of the single-crystal tonite, rhodonite, epidote, tourmaline, calcite, study by adding 0.18° to the 2 €I values. We had molybdenite, sphalerite and galena. The new min- to resort to this unconventional procedure because eral occurs as a late-stage phase in cavities which, of the minimal amount of material available to apart from crystals of helvite and other skarn min- us. Besides, we have previously experienced an erals, may also contain allanite, chabazite, heu- excellent agreement between sets of cell parame- landite, apatite, scorodite, hemimorphite and ters obtained independently from powder and montmorillonite. The mineralogy and paragenetic single-crystal data (e.g. Table 1 in Remming & sequence of this interesting deposit have not been Raade, 1989). Unit-cell data refined from the completely explored. It has been protected by law powder data are a=7.437(2), c=21.79(I)A, V= since 1984 and mineral collecting is now pro- 1205.2(7) A3. hibited. Chemical composition Mineral description Five chemical analyses were carried out with a Kamphaugite-(Y) occurs as platy crystals with a Cameca Camebax electron microprobe operated roughly square outline, rarely up to 1mm across. at 15 kV and 10 nA. The following standards were In some cases the outline is eight-sided, but the used: wollastonite (Ca), pure oxide glasses (Y, Yb, faces are rough and could not be measured. The Er, Gd, Dy) and mixed oxide glasses (Nd, Sm). crystals are platy on {001} and typically form The REE glass standards of Drake & Weill (1972)

682 G. Raade & K. Brastad

Table 2. Chemical composition of kamphaugite-(Y) in erably improved by the description of the new wt.%. minerals lokkaite-(Y), CaY 4(C03)7.9H20 (Pert- tunen, 1971; Nagashima et aI., 1986) and 2 kimuraite-(Y), CaY2CC03k6H20 (Nagashima et aI., 1986). The description of kamphaugite-(Y), CaO 18.4 (0.2) 19.14 Ca2Y2(C03MOH)2-3H20, adds another species to Y203 30.5 (0.3) 38.53 Nd203 1.4 (0.3) this group. Sm203 0.8 (0.3) The formula of tengerite-(Y) has been estab- Gd203 1.6 (0.3) lished as Y2(C03)3.2-3H20 (Nagashima & DY203 2.1 (0.4) Wakita, 1968; Wakita & Nagashima, 1972), later Er203 1.2 (0.1 ) confirmed by the structure determination of Miya- Yb203 1.1 (0.3) waki et at. (1986). Tengerite, lokkaite and CO2 29.6 30.04 kimuraite are structurally related, having ortho- H2O 12.1 12.29 rhombic cells with similar a and b dimensions. 98.8 100.00 The possible arrangement of different kinds of sheets in these three structures has been compared 1. Mean of 5 electron-microprobe analyses (with stand- by Miyawaki & Nakai (1987). The cell dimen- ard deviations). C02 and H20 determined with a CRN sions of kamphaugite bear no resemblance to the analyser. other minerals of the group, and its structure is 2. Theoretical composition ofCa2Y2(C03MOHh-3H20. different (R0mming et aI., 1993). The so-called tengerite from Iisaka, Japan, has been given the tentative formula which was then subtracted, and the H20 and C02 CaY3(C03MOH)3.3H20 (limori, 1938), values were recalculated accordingly (two anal- which is frequently quoted in the literature. The yses of helvite from H0rtekollen with a mean mineral's X-ray powder data were not given, value of 13.17 wt.% BeO were published by but a subsequent investigation has shown that Goldschmidt, 1911). The analytical results with they are similar to those of tengerite proper standard deviations are given in Table 2. The REE (Nagashima & Wakita, 1968). The calcium con-

with odd atomic numbers could not be determined tent may - at least in part - be due to admixed with the microprobe, but may sum to about synchysite, CaREE(C03hF, which has been 1 wt.% REE203. detected by Miyawaki (pers. comm., 1989). It The empirical formula based on C = 4 is: should be noted that the refractive indices re- Cal.9S(Y 1.61REEo.27)L:l.SS(C03)4.00(OH)1.54. 3 .22H20. ported for the Iisaka mineral (a= 1.622, y= 1.642) The inaccuracy in the REE3+ determination is re- are very close to the values for 'tengerite' from sponsible for the low OH- value. The simplified Kazakhstan (Stepanov, 1961); thus, the presence formula is Ca2(Y,REEh(C03MOHh.3H20. The of kamphaugite-(Y) as a possible minor phase mineral dissolves with effervescence in dilute cannot be completely excluded (cf. discussion by acids. Raade et at., 1993). With 2=4, the calculated density is 3.24 gl cm3, in good agreement with the measured value Discussion of 3.19g/cm3. The Gladstone-Dale relationship gi, ~s (with f3set equal to y) a compatibility index On the basis of X-ray powder data (Table 1) and l-Kpl Kc = 0.026, which is in the 'excellent' cate- chemical compositions, there can be no doubt that gory (Mandarino, 1981). It was unfortunately not the minerals reported by Stepanov (1961), Ver- possible to obtain enough material for an infrared woerd (1963) and Hogarth (1972) are identical spectrum, nor for DTA or TGA runs. with the mineral described here as kamphaugite- (Y). However, the tentative tetragonal indexing of Stepanov is not correct, and his density is too low. Relationship to other minerals By comparing the refractive indices, possible var- For ~,long time, the nomenclature of the group iations in composition must be taken into account, of Ga-V-carbonates .has been ambiguous and especially the water content and the OH/F ratio. several minerals have been concealed under the There are indications that the water contents of desigl1ation 'tengerite'. This situation wasconsid- both tengerite and kamphaugite could be variable Kamphaugite-(Y), a new mineral 683

(Nagashima & Wakita, 1968; Miyawaki et aI., Iimori, T. (1938): Tengerite found in Iisaka, and its 1986; R0mming et aI., 1993). chemical composition. Sci. Pap. 1nst. Phys. Chem. Kamphaugite-(Y) from H0rtekollen is a low- Res. (Tokyo), 34,832-841. temperature, late-stage mineral found in cavities; Mandarino, 1. A. (1981): The Gladstone-Dale relation- ship: Part IV. The compatibility concept and its ap- the only younger phase is represented by an oc- plication. Can. Mineral., 19,441-450. casional coating of montmorillonite. It is unlikely Mineev, D. A. (1974): Lantanoidy v rudakh red- that kamphaugite-(Y) was formed by decomposi- kozemelnykh i kompleksnykh mestorozhdenii tion of a precursor mineral, and there is no ob- (Lanthanoids in rare earth ores and in complex vious candidate for such. In the other reported oc- places of origin). Nauka, Moscow, 240 pp. currences, where kamphaugite-(Y) is clearly a Miyawaki, R & Nakai, 1. (1987): Crystal structures of secondary mineral, it forms coatings or fine- rare-earth minerals. Rare Earths, 11, 1-134. Miyawaki, R., Takase, J., Nakai, 1. (1986): Crystal grained masses and not aggregates of distinct chemistry of hydrous rare earth carbonate minerals. crystals as in the H0rtekollen deposit. The crystal structure of tengerite. Abstracts with The anomalous biaxiality of the H0rtekollen Program, 14th General Meeting of I.M.A., Stan- mineral has not affected the space-group symmetry ford, Calif., p. 173. as determined by X-ray diffraction. Foord & Mills Nagashima, K., Miyawaki, R, Takase, 1., Nakai, 1., (1978) have discussed the causes of anomalous op- Sakurai, K., Matsubara, S., Kato, A., Iwano, S. tical properties in minerals. Such anomalies may be (1986): Kimuraite, CaY2(C03)4-6H20, a new min- secondary in nature, originating after crystal erai from fissures in an alkali olivine basalt from Saga Prefecture, Japan, and new data on lokkaite. growth. Mechanical deformation can be ruled out Am. Mineral., 71, 1028-1033. for the freely growing crystals from H0rtekollen, Nagashima, K. & Wakita, H. (1968): On the composition and a rapid temperature or pressure quench produc- of tengerite (in Japanese). Nippon Kagaku Zasshi, ing internal stresses is not very likely. We are thus 89, 856-859. left with a primary cause for the anomalous optical Perttunen, V. (1971): Lokkaite, a new hydrous RE-car- angle, which probably originated from strain in- bonate from Pyoronmaa pegmatite in Kangasala, duced by chemical heterogeneities or structural de- SW-Finland. Bull. Geol. Soc. Finland, 43, 67 -72. fects which occurred during crystal growth. Raade, G., Sa:bl'J, P. C., Austrheim, H, Kristiansen, R. (1993): Kuliokite-(Y) and its alteration products kainosite-(Y) and kamphaugite-(Y) from granite Acknowledgements: We are greatly indebted to pegmatite in Tl'Jrdal, Norway. Eur. J Mineral., 5, H. Austrheim at the Oslo museum for his invalu- 691-698. able assistance with the microprobe analyses, to Romming, C., Kocharian, A. K., Raade, G. (1993): The V. K. Din at the Department of Mineralogy, crystal structure of kamphaugite-(Y). Eur. J Min- British Museum (Natural History) for the H20 and eral., 5, 685-690. C02 determination, and to C. Romming (Depart- Romming, C. & Raade, G. (1989): The crystal structure ment of Chemistry, University of Oslo) for the of natural and synthetic holtedahlite. Mineral. single-crystal study. We are also most grateful to Petrol., 40, 91-100. Stepanov, A. V. (1961): New and rare minerals in alkali R. Kristiansen for contributing his knowledge of granites of Kazakhstan (in Russian). Trudy Kazakh- literature studies. Last, but not least, we thank skogo Nauchno-1ssledovatelskogo 1nstituta Miner- E. Kamphaug for providing material for the initial alnogo Syrya, 5, 147-161. studies. Verwoerd, W. J. (1963): Rare-earth minerals in South African carbonatites. Ann. Geol. Surv. S. Africa, 2, 119-129. References Wakita, H. & Nagashima, K. (1972): Synthesis of tengerite type rare earth carbonates. Bull. Chem. Drake, M. 1. & Weill, D. F. (1972): New rare earth Soc. Japan, 45, 2476-2479. element standards for electron microprobe analysis. Yvon, K., Jeitschko, w., Parthe, E. (1977): LAZY Chem. Geol., 10, 179-181. Foord, E. E. & Mills, B. A. (1978): Biaxiality in PULVERIX, a computer program, for calculating X-ray and neutron diffTaction powder patterns. 'isometric' and 'dimetric' crystals. Am. Mineral., J Appl. Crystallogr., 10, 73-74. 63,316-325. Goldschmidt, V. M. (1911): Die Kontaktmetamorphose Received 7 December 1989 im Kristianiagebiet. Skr. Videnskapsselsk. Kristiania Modified version received 20 February 1991 [Oslo], 1.Mat.-Naturv. Kl., 1911, No. 1,483 pp. Accepted 20 December 1991 Hogarth, D. D. (1972): The Evans-Lou pegmatite, Que- bec: A unique yttrium-niobium-bismuth-vanadium Publication postponed by the author until completion of mineral assemblage. Mineral. Record, 3, 69-77. the companion paper by Romming et at. (1993).