Canadian Mineralogist Yo|.29, pp. 143-148(1991) SOLUBILITYOF GALLIUMIN SPHALERITEAND WURTZITEAT SOOOCAND gOOOC TEIICHI UENO Deportmentof Earth Sciences,Fukuoka University of Education,729Akama, Munakata, Fukuoka, 81141, Japan STEVEN D. SCOTT Departmentof Geology,Earth SciencesCentre, University of Toronto, Toronto, OntarioMSS 3BI ABSTRACT Yamato-74370(EH4) chondrite containsup to 5.8 wt.9o Ga (Nagahara& El Goresy 1984),and that from the (EH3) chondrite,up to 1700ppm Solubilitiesof gallium in sphaleriteand wurtzite were Qingahen (Woolum metal investigatedat 800'C and 900'C by means of phase- Ga et al, 1984).Sphalerite in a sul- equilibrium experiments.In the systemZn-Ga-S, the max- fide nodule of the Qingzhen@H3) chondrite con- imum solubility of Ga in sphalerite is 24,9 atomic 0/oat tains between2.05 and 3.10 wt.VoGa (Rambaldie/ 900'C and 16.3 atomic 9o at 800'C. In the systemZn- ql. 1986\. Fe-Ga-S, gallium solubility is more than2l.4 atomic Vo We have measuredthe solubilities of gallium in in wurtzite at 900oC.more than 15.6atomic goin wurzite sphalerite and wurtzite by synthetic phase- at 800'C, and more than 27.4 atomic 9o in sphaleriteat equilibrium experiments,and here presentresults on 800oC.The cell parametersof Ga-bearingsphalerite and the first study of the systemZn-Fe-Ga-S. Natural Ga-bearing wurtzite decreasedramatically with increasing Ga-bearing zinc sulfide, particularly that in gallium content. meteorites,commonly containsconsiderable Fe, so Keywords: gallium, solid solution, sphalerite, wurtzite, that this systemis of greaterrelevance than the Fe- cell parameters. free systemZn-Ga-S, which had previously been studied ar 900oc by Hahn et ol. (1955). SOMMAIRE SranrlNc Mersntar-s ANDTHEIR SyNTHESIS Nous avons6tudi6 la solubilit€du gallium dansla spha- Three elements(Fe, Ga and S), aIl of 99.9c/oor l6rite et la wunzite i 800oet 900'C en utilisant desexp6- better purity, and three syntheticmonosulfides (ZnS, riencesde synthCse.Dans le systemeZn-Ga-S, la sphal6- materials.ZnS rite peut contenir jusqu'd 24.9V0de Ga (baseatomique) FeSand GaS)were usedas starting a 900'C, et 16.3V0a 800oC.Dans le systdmeZn-Fe-Ga-S, was used as a commerciallyavailable white, pow- la solubilit6 du gallium dans la wurtzite est sup6rieurei deredreagent, in wurtzite form. FeSwas synthesized 21,40/od 900'C et 15.690i 800"C, tandis qu'elle est sup6- by reactingiron and sulfur in an evacuatedsilica glass rieured27 ,4a/odans la sphal6ritei 800oC.Les parambtres tube at 400'C for two daysin order to obtain initial du r€seaude la sphaldrite et de la wurtzite gallifdres dimi- reaction without bursting the tube, and tlen at 5@'C nuent de fagon dramatiquei mesurequ'augmente la teneur for five daysto obtain homogenization.The product gallium. en wasdetermined by X-ray powder diffraction @eKa radiation) to be troilite (FeS). (Traduit par la R6daction) The synthesisof GaS was difficult. Gallium melts Mots-clds: gallium, solution solide, sphal€rite,wurtzite, at 29.8"C, and its liquid does not mix with liquid parambtresr6ticulaires. sulfur, which melts at llgoc, becausea thin layer of gallium sulfide forms at the interface and inhibits further reaction. Despitethis, Klemm & Vogel (1934) INtnolucttoN managed to synthesizeGaS from elementsusing a V-shaped silica tube. Rustamov & Mardakhaev Gallium is found in nature in oxide, silicate and (1964)used an oscillation method to react gallium sulfide minerals (Johan et al. 1983, Bernstein 1986). and sulfur completely.Lieth et al. (1966,1967) syn- The main Ga-containing sulfide minerals are thesizedGaS by sublimation using a silica boat in renierite, germanite and gallite. According to Sheka a long silica tube. et al. (1966), the dominant host of Ga in sulfide ores Our method for synthesizingGaS was as follows. is sphalerite; the concentration of Ga varies between Gallium and sulfur in an atomic ratio of 1 to I were tens and hundreds of ppm. Some high values of gal- sealedin a 2O-cm-longevacuated silica glasstube. lium have been reported in a zinc sulfide phase in The sampletube was heatedfrom 200oCto 850'C meteorites. A zinc sulfide found in the in a furnacethat wasinclined at about 10'; the tem- t43 144 THE CANADIAN MINERALOGIST peraturewas increased by 50'C per day for 14days. This is the polymorph that we synthesized.HP-GaS The sampletube was removed from the furnace a has a high-pressurestructure that can be derived few times a day and shakenin order to mix unreacted from the p structure. e-GaShas a lower symmetry, molten gallium and sulfur. Yellow homogeneous P6m2 (Goodman et al. 1985). Both HP-GaS GaS was obtained. The X-ray powder data for our and e-GaSare metastableforms of GaS, and their synthetic GaS are compared in Table I with those fields of stability are not known precisely.Ifthe heat- for synthetic GaS obtained by Hahn & Frank ing rate is too high during synthesisor the mixing (1955b).Goodman et al. (1985)proposed rhar rhere betweenliquid gallium and liquid sulfur is inefficient, are in fact three polymorphs of GaS: B-GaS,HP- a sugar-like,transparent white crystallinematerial GaSand e-GaS.Beta-GaS is a well-establishedpoly- that has excessgallium metal is produced. This morph that is stableat room temperatureand pres- material is GarSr, as determinedby X-ray powder sure; it crystallizesin the hexagonalspace-group diffraction and electron-microprobe analysis. P6r/mmg, and its unit-cell dimensionsare: a 3.585, Accordingto Hahn & Frank (1955a),GarS, also has c 15.50A lHatrn & Frank 1955b,Wyckoff 1963). threepolymorphs, named o, 0 and 7. Beta-Ga2S3is the disordered,high-temperature phase that has a wufizite structure, 7-Ga2S3is the disordered,low- phase TABLE 1. X-RAY PO{DER-DITFRACIIoNDATA FoF CaS temperature that has a sphaleritestructure, and o-Ga2S3is a superstructurephase with a wurtzite Hahn & Frank (1955b) This study. T0O1-1 structure. The fields of thermal stability of these d(a) r hkl doue(A) d.ar.(A) threephases are not well known. As shownin Table 7.75 st(-) 00? 7 .75 7 .73 2, X-ray data for our Ga2S,agree with those for ct- 3.875 si( - ) 004 3.8?0 3. S66 100 3. 105 st 100 3.100 3.101 GarS, obtained by Goodyear et al. (1961). 3.044 st 3.036 3.047 2.882 ss 1,O2 2.878 2.A7A I z.oor n 103 2.653 2.657 2 2.5B3 s 006 2.5?6 2.177 t7 2.423 s-h 104 2.419 2.4t9 1 SvNrHsrrc PHASE-EeurLrBRruMExpEnrMsNrs 2.194 e(+) 2.!A? 2.190 1.986 ss 106 1.9831 1.9820 I IN THE SYSTET4Zn-Fe-GA-S t .938 ssg 008 1.9333 1.9328 1.803 st(+) 707 1. ?989 I .7992 11 1.793 st 110 1.?89? 1.?905 7 Meteoritesthat. contain a Ga-bearingzinc sulfide 1.746 ss( -) tt2 7,7445 I.7443 1 .644 108 1. 6399 1 .6403 contain metallic iron and troilite and, therefore, have I.627 s-n L8247 1..8247 1.552 ss(- ) 200 1.5516 1.5506 formed at a low sulfur fugacity. Thus, many of our 1.550 00rQ 1.5465 1.5462 experimentsincorporated an FeS + Fe buffer. Five hex. hex. assemblagesof starting materials were used: a 3.585 A a 3.5810(?)A (ZnS (ZnS c 15.50 A c 15.462(3) A A: + GaS) + 2(FeS+ Fe), B: + 2GaS) + 2(FeS * Fe), C: (ZnS + 4GaS) + 2(FeS + Fe), D: ZnS + GaS + FeS,and E: ZnS + 2GaS.Starting materials were mixed by grinding in an agate mor- TABLB 2. X-RAY POXDER-DITFRACTIOS DATA FOR a-GaaSs tar and were sealedin evacuatedsilica tubes.These Coodyea! ot al,. (1981) ThtE study, T026 wereheated in an electricfurnace at 900oCor 8fi)oC d(A) dore(!) da.r6(A) and were quenchedin cold water after heating for 5.33 tsa 110 5.34 20 13 to 4l days (900"C runs) or for 26 to 56 days 4,?7 ts 200 4.775 4. ?6S 1B (800oC 4.?3 n 1tl 4.732 4,724 7 runs). 3.515 w 3:.1 3. 518 Products were examined by reflected light 3.488 m 202 3.496 3.494 3.209 vE 020 3.21,5 3.Ztr ts4 microscopy and by X-ray powder diffractometry 3.010 a 402 3.014 r00 2,844 tu 310 2.444 2,A4A (Mn-filtered FeKo radiation), with Si as an internal 2.924 Ba Lt2 2.430 2,424 25 parameters 2,742 m 027 2,744 2.749 standard. Cell were calculated for some 2.654 i(b) 220 2.883 2.863 4 phasesby the least-squaresmethod from precisely ooz 2.65S 2,457 2.378 w 400 2,344 2.344 I measuredd-values. The phaseassemblages produced 2.353 vt 222 2,343 2.364 1 Z,2OB ts 511 2.205 2,209 are shownin Table 3. The chemicalcompositions of z.LSg r 203 2,197 phases 2. 185 w 2. 190 2.LSO the weredetermined with an ETEC electron ?.098 eF 2.toz microprobe using metallic iron, GaP, synthetic 2.085 @ 2 .089 2.0s0 2.O4O r 2,046 sphaleriteand synthetic troilite as standards.The 1.S03 w(b) 1.884 vt 1 .8868 analyticalresults, each an averageof severalgrains, 1.451 v6 2e L.424 r are shown in Table 4. All analytical errors are within 1.810 yw 0.1wt.9o. a 12.637A a L2.452<4>A b 6.41r A b 0.421.(3)a c ?.03e A c 7.044<2, A (Fe,Ga) alloy 9:131.0?(3)" b:latho! broad An alloy of Fe and Ga was obtained in runs T009, GALLIUM IN SPHALERITE AND WURTZITE 145 TABLE3.