Canadian Mineraloslst Vol. 14, pp. 387-390 (197Q

ZEMANNITE,A ZINGTETLURITE FROM MOCTEZUMA, SONORA, MEXICO

J. A. MANDARINO Department of Mineralogy and Geology, Royal Ontario Museum, L00 Qaeeds Park, Toronto, Ontario, Canada E. MATZAT Mineraloglsch-krlstallographisches Institut, University of Gdttingen, Gdttlngen, Gennany S. J. WILLIAMS Pera State College, Pera, Nebraska, U,S-4.

ABSIRAG"I fesseurJosef Zemann,de I'Universit6 de Vienne, qui a contribu6 tellement i nos connaissancesdes struc- Zemannite occurs as minute hexagonal prisms tures des compos6sde tellure. terminated by a bipyramid. The mineral is light Clraduit par le journal) to dark brown, has an adamantine lustre, and is brittle. It is uniaxial positive: Crystal structure study the fol- Zemannite was first recognized as a possible group P6s/m, a 9.4t!0,42, c 7.64! lowing: space new species by Mandarino & Williams (1961) tellurite 0.024, Z:2. Zemannite is a zeolite-like who referred to it as a zinc tellurite or tellurate. with a negatively charged framework of lZtu Problems involving the determination of the GeOrLl having large (diam. : 8.28A) open chan- nels parallel to [0001]. These channels are statis- chemical formula delayed submission of the tically occupied by Na and H ions and possibly by description to the Commission on New Minerals H:O. Some Fe substitutes f.or 7m, Partial analyses Names, I.M.A. After the structural determina- and the crystal structure analysis indicate the for- tion by Matzat (1967), the description of zeman- mula (Zn,Fe)2(feOs)sNafir-']HzO. Strongest lines nite was submitted and both the mineral and in the X-raL powder pattegl (in A, for CuKa) are: name were approved.An abstract of the descrip- 8. l5(1 0) ( 1010), 4.07(8) (2020), 2.96(6) (1122), 2.845 tion of zemannite was published by Mandarino 6) QLTD, 2.778(' (2frD, t.726(6)QO.4,224r. et al. (L969). The mineral is named in honor The name is in honor of Professor Dr. Josef Ze- of Professor Dr. Josef Zemann, esteemedAus- 6snn, IJniversity of Vienna, who has contributed trian crystallographer who has contributed so so greatly to our knowledge of the structure of greatly to oul knowledge of tellurium and sele- tellurium compounds. nium oxysalts. Type material (milligrams) is preservedin the mineral collections of the Royal SouvrernB Ontario Museum. The type specimen is ROM La z6mannite se trouve sous forme de petits Number M25933. prismes hexagonaux bipyramidaux. Ir minlpl y6- rie du brun pile au brun fonc6; son lustre est ada- mantin. Il est uniaxe positif (@-1.85, e-1.93) et OccrrnnrNcs AND PrrysrcAr, PRopERTEs relativement fragile. Sa densit6, sup6rieure b 4.05 g/cm3, se rapproche probablement g/we. de 4.36 Zemannite mine, Une 6tude de sa structure cristalline r6vdle le groupe occurs at the Moctezuma near Moctezumao Sonora, Mexico. Although the spatial P6s/m, ayec a 9.4L!0.02, c 7.64+0.021\ Z:L La z6mannite est un tellurite'26olitique" qui individual crystals are very small, zemannite is consiste d'une trame lZng(feOs)s] ] charges n6ga- widespread at tle locality. The occurrence is tives et de canaux d'un diamdtre de 8.28A paralld- described by Gaines (1965) who has also sum- les d [0001]. Ces canaux contiennent des ions Na marized the mineralogy of the locality (Gaines et H et m6me peut-Otre de l'eau. Le fer substitue 1970). pour le zinc. Des analyses partielles ainsi que l'ana- Zemannite occurs as small crystals, usually lyse de la structure donnent la formule suivante: less tlan one mm long, which consist of a prism (7n,Fe)r(IeOs)sNa,H2-.yH2O. Les raies les plus in- and a bipyramid. The crystals are translucent to tenses dans un ctch6 de .goudre (en A, _radiation transparent, light to dark brown, and have an (1010), C\rKa) sont: 8.15(10) 4.07(8)Q020), 2.96 adamantine lustre and a white streak. Zemannite 6)0rzD, 2.545(qQED, 2.778('(n2D, r.726 does not fluoresce under short- ot long-rpave 6) Q014,224r.Ie nomfair honneuri M. le pro- ultraviolet light. No cleavage was observed. The 387 Downloaded from http://pubs.geoscienceworld.org/canmin/article-pdf/14/3/387/3420048/387.pdf by guest on 30 September 2021 388 TTIE CANADIAN MINERALOGIST

hardness was not determined, but the mineral Zemannite is uniaxial positive with or=1.85 is quite soft and is very brittle. Although the and e-1.93. The mineral is dichroic with or red- density could not be measured, it was calculated dish brown and e yellowish brown; absorption, to be about 4.36:L0.08 glcn8. The method of .ole. calculation is given in a later section. Cnvster.r.ocnepgy Zemannite is hexagonal, space gf,oup P6s/ m - Cab a 9,4I:O,02, c 7.64f.0.O2A, c;a = 0.8119, I/-585.9A8, Z=2. T\e crystals are moryhologically simple and consist of only two forms: {1010} and {10i1}. The habit is usually prismatic, but a few crystals with a very small prhm development have been seen. No twinning was observed. The angular relations of the two - forms are: {10f0}, O 30' oo,op = 90o 00t; - {1011} 0 30' OO',p 43" O9t.A typical crystal is shown in Figure 1. Full details of the structure of zemannite are given by Matzat (L967). The X-ray powder dif- fraction data are grven in Table 1.

CHEMTcaL CotvtposrtroN A complete chemical analysis was not per- formed. Partial XRF and electron microprobe FIG. 1. A typical crystal of zemannite showing the analyses indicated that the atomic ratio of Zn forms ane {1010} {10T1}. to Fe is between 3:1 and 3:2. The atomic ratio 'I. of (Zn*Fe) to Te is about 2t3. Small amounts TABLE X.MY POI{DERDATA FOR ZEMANNITE of Mn, Mg, and Na were detected, but do not exceed one percent each. 'r '10 'l0Trolo 8.r50 8.15 3143 4 The structural determination by Matz.at (1967) s.5i4 3282 rr!o 4.705 showed that zemannite is a zeolite-like tellurite \z so50 'I 2020 4.075 B 21tr4 with a negatively charged framework of Zna rrZl 4.006 4'152 1 00!2 3.820 3.80 3 soSt (IeOr), with a large (8.28A diameter) sftannel 2021 3.594 40tI3 2 running parallel to [0001]. These shannels are r oT2 3.458 3.44 1 336-0 2r30 3.080 3.07 4 30-34 \z statistically occupied by Na and H ions and 1122 2,966 2.96 6 4260 possibly by HeO. Partial analyses and the 2r3l 2.857 I .645 6 JJb I \z zo72 2.788 2.178 9 4261 crystal structure analysis suggest the formula 3o3o 2.717 SaaJ (Zn,Fe)z(IeO:)aNa"Hr"'IHrO, where .r can vary 3o3r 2.560 ? 1oJ5 r ol3 2.431 5052 from 0 to 2. Type material is ferroan zemannite. 21i2 2.398 ?.390 3 2244 zz4o 2.352 z.J4a 5 5rq0 3i40 2.260 3r94 1.459) 2241 2.248 4153 1.4581 I .455 Celcur,lrroN oF DENsrry lr 23 2.240 2.242 rlz 1.453) 3032 2.214 2.207 4 3&2 'I1.451 Because of the small size of the crystals, it 3rlr 2,168 5r0l .438 2023 2.I60 2.160 5 r.431 was not possible to measure the density of the 4oEo 2.038 4zdz 1.428 2242 2.003 1 1.393 mineral. A crystal placed in a liquid with a 4oAr r.969 t3g3'I1.373 density of 4.05 g/cm3 sant, thus establishing 1.963 2115 'I.369 3rf2 1.946 Y; 5192 .367 the fact that the density was greater than 4.05 0094 'II.9t0 2 6060 I .358 glcml. The density of zemannite was calculated 3250 .870 4370 I .340 r oI4 r .860 6oEl in the following manner. 'r I J 'I 3013 .858t 3254 'I.336 From tle unit cell dimensions and the formu- 325r 1.8i6 'I.336 4042 I .798 4 3035 '|.332 la (Zn,Fe)z(IeOs)aNaJIz*'yHrO, it is obvious 415o 1.778 $71 .320 that a range in densrty can be calculated for nA 1.770 v" 4263 'lI .318 I .316 4t5t '11.732 szlo 305 each value of y varying the value of .r between zo14 .7301 1.728 | 0 and 2. The lower limif sf this range is 3.705 g/cme .r=0 y-0; i.e, the formula Cu.traradiation, camera dlam. ll4.6m, m€asurenents corrected where and for film shrlnkago, RoMspeclnen numberltl?5933, fllm No, 3477. is (Zn,Fe),CIeOa)'H, (the amounts of Zn and

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TABLE2. SAmPLECALCULATToN 0F THE DENSITy 0F (Znr.ruFeo.uu)(reOr)rNatr.SHrO

Constituent 1,1t.%=p k pk/100 Denslty frcm Gladstone-Dalerelationship 'I 'l Zn0 4. 35 0. 58 0,0227 o -';t " - 4.g8s/cm3 Fe0 6.10 0.188 0.0115 ## TeO, 62.55 0.183 0.'l't45 Density from unit cell NaZ0 4.05 0.190 0.0077 o-ffi- l!!8#- 4.34s/cm3 Hzo 12.95 0.340 0.0440 u - nolecularweight Total I 00.00 0.2004 z - numberof formulaunits per unit cell tp765.45 x-0.200 Y - volumeof unit cell 4 = Avogadro'snurnber (0.6023x1024)

Fe in the formula ate, respectively 1.35 and of various compsitions in two ways. First, the 0.65 throughout this discussion. This is equiva- density wascalculated in the usual way from the lent to an atomic ratio for Zn:Fe of about 2 to unit-cell parameters.Next, the density was cal- 1). There is no upper limit if it is assumed that culated from the Gladstone-Dalerelationship. y can vary infinitely. Obviously, there must be n-r used is p : where p is a limit to the number of water molecules that The formula K , can be accommodated in the channel Without density, Z is the meanreftactive index, and K is going into this question, however, it is possible the specificrefractive energyof the mineral. The to calculate a probable upper limit for the mean refractive index for a uniaxial mineral to reduce the density of zemannite and, further, : range in density. such as zemanniteis given by the tormula,T .s-t2,., -L.E . The value of K must be calculated The approach was to calculate the densities J

F (t, z lrl o lrl J o I lrl o= oF o J (9

3.50 4.OO 4.5O 5.OO UNIT CELL DENSITY Frc. 2. Unit sell densrty versus Gladstone-Dalodensity qf (7n1.asFe6.es)Cfeos)aN%Hr*'lHao,for various values of r and y.

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ftom tle weight percentagesof eachconstituent AcrNowr,nncuvrENTS for a particular mmposition and from the spe- The writers wish to thank D. cific refractive energiesof those constituents. IUr. B. Sturman who prepared Figure 1, Mr. D. R. McKinnon The formula for this relationship is: /l : prepared bh who Figure 2, and Miss IL Driver who hrft, + kzqz +, ...ffi. Here,kt, k' typed the manuscript Dr. D. C. Haris provided i6ti ffi partial XRF analyses. etc. are the specific refractive energies of the constituents and Pr, fu etr. are tJre weight per- RSF.ERBNCES centages of the constituents. The values of the (1965): &'s used in these calculations are those given by GAr\rEs,R. V. Mineralizacion de telurio eu la mina Moctexuma, Mandarino (1976). A sample cerca de Mocteznrma,So calculation for an tora. Univ. Nat. Auton. M€xico, Inst. Geol. Bol. assumed composition of (Znr.arFeo.as) (TeOs)g 75, Pt. l. NaH . 5 H:O is given in Table 2. -, (1970): The Moctezumatellurium de- The values of the two densities were calcu- posit. Mineral. Record L, 4043. lated for various compositions and are plotted Meroenmo, J. A. & Wu-LraMs,S. J. (1961): Five against each other in Figure 2. T:he composi- new minerals from Moctezuma, Sonora, Mexico. tional limits of zemannite are represented by a Sclcncet33,2Ot7. band running from upper left to lower righl , MarzAT, E. & Wn-r-reus, S. I. (1969): The width of the band is governed by the value Znmqnnite, a new tellurite mineral from Moc- of .;r. The length of the band is determined by t€zuma, Sonora, Mexico. Can. Ml,neral. 10, 139- the value of y. The line at 45o to the soordinates 140 (Abstr.). represents points where ttre "structural" den- -, (1976): The Gladstone-Dalerelationship. sities are equal to the "Gladstone-Dale" den- Part Ir Derivation of new constants.Can. Min- sities. This line intersects the band at 4.28 eral. (in press). g/cma and 4.44 g/cm'. The density of zeman- MArzAT, E. (1967): Die Krista[struktur eines un- nite is probably between these two values. The benannten zeolithartigen Telluritminerals, {(n, averageof these values is 436 g/clor3.In Figure Fe)rfIeOrl")NaJIz-.]HeO. Tschermaks Mlneral 2, this density correspondsto a composition of Petrog. Mitt. XU, 108-117. (Zn,Fe),(f eO.)rl.[aH.5. 2HrO. Manuscript received March 1976.

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