American Mineralogist, Volume 79, pages 1003-1008, 1994

Mineralogical studies of the nitrate deposits of Chile: YII. Two new saline minerals with the composition&(Na,K)oNa.Mgro(XO4)rrGO t)'r'l2HrOz Fuenzalidaite (X : S) and carlosruizite (X : Se)

Juorrn A. Kor.rNnnr,Howlno T. EvaNs,Jn., Jnvrns J. McGrp, Gnoncr E. Enrcxsm U.S. Geological Survey, National Center 959, Reston, Virginia 22092,U.5.A.

ArsrnLcr Two new isostructural saline minerals from the nitrate deposits of northern Chile have the composition IQ(Na,K)oNa.Mg,o(XOo),r(IOr),r. l2HrO: fuenzalidaite(FNZ, X : S) and carlosruizite (CLR, X : Se,S,Cr).They are trigonal, P3cl; for FNZ c : 9.4643(4), c : 27.336(6)A; for CLR a: 9.5901(8),c:27.56(2) A. The crystalsform thin hexagonal plateson {0001} up to 0.2 mm across,beveled at the edgesby {1012}. The crystalsare transparent and pale yellow; optics are uniaxial negative with <^r: 1.622(5),e : 1.615(5) (FNZ), and co: 1.655(3),e : 1.642(l) (CLR). The crystalstructure (R* : 0.043 for FNZ, 0.053 for CLR) consistsof two complex slabsnormal to the c axis, each having a double layer of iodate groups (IOr), bounded at the top and bottom by layers of SOo or SeOn g.roups.The strongestX-ray powder lines [d, (1, hkl)l for FNZ are 13.67 (50,002), 7.05 (40,102),3.927 (100,202),3.023 (41,212,117),2.681 (33,302); for CLR, 13.75(30,002), 7.10 (20,102),3.56t (100,204),3.082 (32,206), 3.058 (39,2t2,tt7),2.715 (39,302).

Ixrnooucrrox OCCTTNNTI\ICE AND ASSOC:IA'TED MINERAI^S The two new minerals, fuenzalidaite (fwen-zaJeed'-a- Small amounts (a few tens of milligrams each)of fuen- ite) and carlosruizite (kar-los-ru-eez'-ite),are members of zalidaite and carlosruizite were found in nitrate ore from a solid solution series,IQ(Na,K)oNauMg'o(XO4)', (IO3)',' two localities in the Chilean nitrate fields. Fuenzalidaite l2HrO, for which the end-membershave X : S for the occurs as blebs and flattened aggregatesofbright yellow former and X : Se for the latter. With the exception of micaceousmaterial in veins and veinlets of white nitrate Se,the componentsof theseminerals are widespreadcon- ore, called caliche blanco, in a former nitrate mine about stituents of the Chilean nitrate ores. Se was not known to I km south of the former plant site of Oficina Santa Luisa. occur in these ores until it was discovered as a major Carlosruizite was found as -200 pm platy crystals in component in carlosruizite by X-ray spectroscopyin the samplesof iquiqueite, Na.KrMg(CrOo)BroOrr(OH)'l2H2O scanningelectron microscope (SEM). Subsequentanaly- (Ericksen et al., 1986), obtained by leaching caliche sesofseveral specimensofnitrate ore from scatteredlo- amarillo (yellow nitrate ore) from samplesin the Iquique calities in the Chilean nitrate fields showed them all to office of the former Servicio de Minas del Estadoof Chile, contain Se in amounts ranging from a few parts per mil- now the Servicio Nacional de Geologia y Mineria. The lion to nearly 50 ppm. field locality of these samplesis not precisely known but The new minerals are named for Humberto Fuenzalida probably is in the vicinity of Z,apiga,where caliche ama- P. (1904-1966)and Carlos Ruiz F. O. l9l6);both played ril/o is especiallyabundant. major roles in the 20th century development of geology Among the 25 speciesof saline minerals that have been in Chile. Ruiz planned and directed the first national geo- identified in the Chilean nitrate ores (Ericksen, 1993), I I logical institution (inauguratedin 1957), the Instituto de are known to be associatedwith the two new minerals InvestigacionesGeol6gicas, now the Servicio Nacional de reported here. Veins and veinlets containing fuenzalidaite Geologia y Mineria, which beganthe first systematicgeo- consist chiefly of a fine-grained mixture of logic mapping and study of mineral deposits in Chile. (NaNOr) and ; tiny blebs of fibrous probertite Similarly, Fuenzalida planned and directed the first school [NaCaBrOr(OH)o. 3HrO] and platy darapskite[Nar(NOr)- of geology in Chile (inauguratedin 1958) at the Univer- (SO").HrO)l occur in cavities. The fractured bedrock in sity of Chile. The two new mineral speciesand names which these veins occur also contains abundant veinlets have been approved by the Commission on New Min- of anhydrite (CaSO"). The dense caliche amarillo con- erals and Mineral Names of the IMA. taining carlosruiziteconsists chiefly of a fine-grainedmix- 0003404x/94109I 0-l 003s02.00 1003 1004 KONNERT ET AL.: zuENZALIDAITE AND CARLOSRUIZITE

Tlau 1. Crystallographicdata for fuenzalidaiteand carlosruizite

Fuenzalidaite Carlosruizite

Formula GMlNa6Mglo(XO1I2(lO3),r. 12HrO Cations M (Kr rNarr) (K14Na26) x (So*Seo*) (Seo sso $Cro,o) Formula weight 4225.8 4520.1 D* g/cmg 3.2U 3.400 Optical properties Color transparent,pale yellow Character uniaxial(-) uniaxial(-) Refractiveindices @ 1.622(5) 1.655(3) e 1.615(s) 1.6420) Crystallography Spacegroup PJcl P3,c1 Unitcell data a (A) 9.4643(4) 9.5901(8) c(A) 27.3it6(6) 27.s612) v(4.) 2120.s(41 2195.0) z 1 1 cla 2.888 2.877 Morphology thin, hexagonal plates {0001} bounded by {10T2} Structure analysis Diffractometer modified Picker automatic Radiation Nb-filteredMoKa (0.7107 A) Absorption coeff. tt (cm-1) 52 76 Crystd dim. (mm) 0.12x0.12x0.020 0.24x0.12x0.013 Range of 2d (") 4-40 4-50 ReflectionsMeasured 2078 3864 Independent 704 1325 For refinem. 520 691 Reliabilitytactors R 0.0&t 0.087 R* (1/o na) 0.043 0.053 Goodness of fit 1.76 1.86

ture of nitratine, halite, and darapskite. The residuesof Cnysr.qlr.ocRAprry AND srRUcruRE ANALysts leaching this material in cold water contain dietzeite Although the crystal morphology of both fuenzalidaite (IO,), (CrOo)], briiggenire . [Ca, [Ca(IO3), H,O], tarapa- and carlosruizite is rhombohedral, single-crystal X-ray caite (KrCrOo), lopezite (KrCrrOr), [NaCa- precessionphotography shows a primitive trigonal lat- B506(OH)6.5HrOl, probertite, and (CaSOo. tice. The two crystals are isomorphous, with the same 2H,O). flat, hexagonal habit (Fig. l) and very similar crystallo- graphic properties. The precessionpatterns show sym- pRopERTTES Prrysrclr- AND oprrcAr, metry and extinctions of the spacegroups P3cl or P3c; Fuenzalidaite and carlosruizite occur as thin, colorless the former centrosymmetric group (no. 165) was fully to pale yellow, transparent, euhedral, platy crystals with confirmed by the subsequent structure determination. hexagonal outline, generally <200 p,m in diameter and Unit-cell parameters (Table l) were refined from X-ray 20 pm thick. The crystals have a pseudorhombohedral powder data obtained with the Guinier-Hiigg focusing habit, flattenedon {0001} with bevelededges {10T2} (Fig. camera (Table 2). l). They are slowly soluble in HrO. Scanning electron Single-crystalintensity data for both crystals were col- micrographs(Fig. l) show that some crystalshave regular lected with a Krisel-modified Picker automated diffrac- fractures parallel to { I 1201that may mark cleavageplanes. tometer. After application of the usual corrections for Surfacesof some crystals show abundant round or elon- Lorentz-polarization and absorption (by Gaussianquad- gate cavities (Fig. lB), which probably were formerly filled rature) and normalization to ,E values, the -F data for with saline fluids. The crystalsare brittle and break easily carlosruizite were used for a structure analysis. At the into multiple fragments. Hardness could not be mea- outset, the chemical formula was unknown, but an X-ray sured, but to judge from the easeofbreaking, it is on the spectroscopictest in the SEM showed the presenceof I, order of 2-3. The luster is vitreous. S, K, Mg, Na, Cr, and even Se. Both minerals are uniaxial negative. Their refractive Starting with the Se-rich carlosruizite crystal, the first indices, measured with Na light by immersion on the E map derived from a Multan analysis at once revealed spindle stage,are given in Table l. Determined on the the position of the I atom. Subsequently,each of the con- basis of the structural formulas defined in Table I and stituent atoms (identified from electron density and co- the molar refractivities listed by Mandarino (1976), the ordination considerations),K, N4 Mg, and finally O, ap- Gladstone-Dale compatibility for fuenzalidaite is good, pearedin turn, in structure-factorelectron-density cycles, and for carlosruizite, fair (Mandarino, l98l). until the whole structure was clearly revealed.This pro- KONNERT ET AL.: FUENZALIDAITEAND CARLOSRUIZITE 1005

TABLE2. X-ray powder data for fuenzalidaiteand carlosruizite

Fuenzalidaite Carlosruizite d*" (A) d*" (A) ilh d* (A) 4* (A) ah 002 13.67 13.67 50 13.79 13.75 30 102 7.03 7.05 40 7.11 7.10 20 104 5.249 5.254 4 s.303 111 4.663 4.665 13 4.724 113 4.200 4.200 3 4.251 200 4.098 4.099 I 4.153 202 3.926 3.927 100 3.976 3.974 16 204 3.515 3.515 24 3.557 3.561 100 210 3.098 3.099 16 3.139 211 3.078 3.078 I 3.119 3.112 3 206 3.047 3.048 I 3.080 3.082 32 212 3.021 l 3.023 41 sos' 39 117 3.012 | 3:3fl1) 214 2.822 2.822 4 2.857 2.860 2 2.756 0,0,10 2.734 ) 2.731 1 300 2.732 | 2.768 302 2.679 2.68',1 33 2.714 2.717 39 208 2.624 2.624 2 2.651 304 2.537 2.537 10 2.569 2.570 12 217 2.4270 2.4269 <1 2.454 220 2.3661 2.3665 2 2.398 222 2.3314 2.3273 21 2.362 2.361 14 223 2.2901 2.2905 6 2.320 2.323 4 311 2.2654 2.2654 9 2.2955 2.2948 5 312 2.2424 2.2434 2 2.2719 2.2713 4 224 2.2359 2.2348 <1 2.264'l 313 2.2056 2.2060 <1 2.2343 2.2378 2 219 2.1688 2.1691 <1 2.1919 314 2.1570 2.1575 I 2.1254 2.1256 2 308 2.1339 2.1329 1 2.1579 315 2.0990 2.0993 2 2.1254 2.1256 2 2,1,10 2.0497 2.0490 <1 2.O710 402 2.0264 2.0261 <1 2.0531 2.0543 4 2,0,'t2 1.9911 1.9957 1 2.OO97 404 1.9628 1.9634 2 1.9884 1.9879 4 320 1.8804 1.8802 3 1.9054 1.0925 1 406 1.8688 1.8692 2 1.8920 322 1.8628 1.8624 12 1.8869 1.8875 12 Fig. l. Scanningelectron micrographs of (A) fuenzalidaite, 323 1.8416 1.8415 <1 1.8657 and (B) carlosruizite.The scalebars at the lower right corners 2,1,12 1.8353 1.8354

TleLe 3. Structural parametersfor fuenzalidaiteand carlosruiz- TrEu 7. Compositions of fuenzalidaiteand carlosruizite ite Fuenzalidaite Carlosruizite Sile m Theor. Probe. m Theor. Probe' 't29 I FNZ 0.3904(3) 0.2218(2)0.4s51(1) 0.075(8) K"O [ 7.2 8.0 s.9(2) 7.4 7.7 6.7(21 cLR 0.3911(2)0.2199(2)0.4560(1) 0.105(s) Na,O 26 .l 8.8 6.5 5.2(1.21 8.6 5.9 4.7(4) o1 129 FNZ 0.195(2) 0.03s(2) 0.4557(7)0.11(2) Mgo 9.5 10.0(5) 10 8.9 e.2(3) cLR O.2O1(2) 0.039(2) 0.4585(6) 0.10(2) [10 SO" [11.002O.7 20.9(9) 4.4 7.8 7.9(5) 02 129 FNZ 0.490(2) 0.159(2) 0.4057(6)0.11(2) SeO. 12 0.3 1.1 0.1(2) 6.4 18.0 1e.0(8) cLR 0.489(2) 0.168(2) 0.4097(7)0.13(2) 1 't2g CrO3 [ 0.7 1.7 0.2(1) 1.2 2.6 2.5(21 o3 FNZ 0.481(2) 0.169(2) 0.5085(7)0.13(2) l.ou 12 47.4 49.3(1.0) 12 44.3 4s.6(9) cLR 0.482(2) o.'t74(21 0.5060(7)0.14(2) HrO 12 5.1 12 4.8 S(Se) 129 FNZ 0.3184(8) 0.2986(8) 0.324s(3) 0.10(2) Total 91.6 95.6 cLR 0.3188(5) 0.2992(s)0.3243(2) 0.11(1) o4 129 FNz 0.288(21 0.416(2) 0.2992(6)0.11(2) /Vote.'m denotes cations per unit cell trom structure analysisbased on cLR 0.286(2) 0.427(21 0.2e75(7) 0.14{2) formulas given in Table 1. Probe analysesshowed trace amounts of Ca, 05 129 FNZ 0.220(21 0.135(3) 0.3044(7)0.16(2) Al, and Si. Standardsfor probe analysis; Na,Al,Si;albite (Tiburon);Mg,Cr, cLR 0.223(2) 0.126(2) 0.3031(6)0.11(2) chromite ffibaghi); S, anhydrite;Ca,l, bruggenite;K, orthoclase; Se, SeS, OO 129 FNz 0.500(2) 0.354(3) 0.3212(710.1512) (synthetic). cLR 0.507(2) 0.365(2) o.32o4(7) 0.14{2) ' Electron microprobe analyses (wf/") average of ten spot analyses each, 07 129 FNZ 0.274(2) 0.2s5(21 0.3805(7) 0.12(2) standard deviationsof ten observations in parentheses. cLR 0.274(21 0.2s4(2) 0.3801(7) 0.14(2) K1 6f FNZ 0.3789(10)0 l/a 0.15(3) cLR 0.3eH(10) 0 1/q 0.'17(2) M(Na,K) 4e FNZ O 0 0.1238(7)0.19(3) CLR O 0 0.1212(s)0.1s(3) closedby layers ofsulfate groups above and below. These Na1 4d FNZ V3 % 0.33ri]6(7)0.14(3) K cations, and the lay- CLR V3 % 0.3338(7)0.1s(2) compound layersare separatedby Na2 2a FNZ O 0 V4 0.11(5) er complex itself is held together by Na and Mg cations CLR O O v4 0.11(3) (Fig. 2). All the cations have normal coordination and Mg1 4d FNZ Vg 2h 0.1394(5)0.12(3) CLR 1/s % 0.1391(6)0.12(2) bond lengths with O (Table 8). The average S-O bond Mg2 4cl FNZ Vs 4 0.4478(6) 0.12(3) length in fuenzalidaite is 1.505 A, close to the value of 1/s CLR % 0.4480(6)0.12(2) 1.489A in thenardite(Mehrotra et al., 1978).In carlos- Mg3 2b FNZ O 0 0 0.07(71 CLR O 0 0 0.13(4) the tetrahedral bond length is 1.590A, about % of o8(H,O) 129 FNz 0.667(2) 0.504(2) 0.1020(6) 0.04(6) the differencebetween the S-O lengthof 1.489A and the cLR 0.662(2) 0.497(21 0.0987(7)0.14(2) Se-O length of 1.633 A in NarSeOo(thenardite structure: /Votej FNZ : tuenzalidaite;CLR : carlosruizite,u: rms displacement Mehrotra et al.. 1978). (A). The trigonal-pyramidal IO, group has an averageI-O bond distanceof 1.863A in fuenzalidaiteand t.797 Ain carlosruizite, as compared with 1.806 A in NaIO, (Svens- Cnnnncnr, coMFosrrroN son and Stahl, 1988).The averagepyramidal angleis 96.7' After the analysis of carlosruizite was in fuenzalidaite,97.3'in carlosruizite(Table 8), and 100.5" completed,the chemicalcompositions of fuenzalidaiteand in NaIO, (Svenssonand Stihl, 1988). The pyramidal io- carlosruizite were deterrnined by electron microprobe date groups stand in a layer with one base edge nearly analysisof single crystals(Table 7). The crystalswere too parallel to the c axis (Fig. 2). In this structure, as in those soft to be embedded in plastic and polished in the usual of other iodates, a large cavity is present in the iodate manner and were mounted flat on an Al stub, thus pro- layer centeredopposite the I atom at the apex ofthe IO, viding a uniform, horizontal surfbce for electron probe pyramid, which accommodatesan unsharedelectron pair. analysis. The nearestI-O distancesopposite the pyramid vertices The lack ofprecision in theseanalyses probably results are>2.70 A. from the use of soft, unpolished crystals, the presenceof The Na atoms have octahedral coordination at sites HrO of crystallization, and volatilization of material Nal and Na2, with an averageNa-O distance of 237 A causedby exposureto a vacuum and heating in the elec- (Table 8). Mg is also octahedrally coordinated at Mgl, tron beam, the last being the most important (seeErick- Mg2, and Mg3, with an averageMg-O distance of 2.09 senet al., 1986).Molar ratios for Mg, S, Se,and I are not A. ttre unexpected appearanceof Na in the M site is significantly different from those predicted by the crystal actually quite reasonable.Although the eightfold coor- structure analysis, but those for K and Na are consider- dination of site Kl is less than that of ninefold-coordi- ably less than expected.The low values found for K are nated M, the averageK-O distance in the former (2.90, attributed to extensive substitution by Na at a putative 2.% A) is normal for K atoms; the averagedistance at K site (M), and the low values for Na are attributed to the M site (2.79,2.71A1, however,is substantiallyless volatilization. than expectedfor K and is consistent with partial occu- pancy by Na. Thus it is apparent that it is the Na content Cnvsrlr. cHEMrsrRY that is deficient in the microprobe analysis(Table 7), not The crystal structure of fuenzalidaite and carlosruizite the K content. may be viewed as a double layer of iodate groups en- The HrO molecules form the face shared by the Nal KONNERT ET AL.: FUENZALIDAITE AND CARLOSRUIZITE 1007 T t/o o o d z= K, Na

Na, SOo o Mg Na, K(M) Hzo

Mg, IO. L/2 z: ME

Mg, Io,

Hzo Na, K(M) Mg

Na, SOo

z:'/o K, Na

r:0 Fig.2. One layer of the fuenzalidaiteand carlosruizite structure viewed along the a axis. Solid circles are I (in IOr); SOo(SeOo) Sroups are represented by shaded tetrahedra. The octahedral coordination of Na and Mg cations on the threefold axes is shown by dashedlines; layers are separatedby Kl and Na2 atoms.

TleLe 8. Bond lengths (A) and angles (') in fuenzatidaite(FNZ) and cartosruizite(CLR)

t-o1 1.81(2) 1.79(2) o1-r-o2 e7(1) 100(1) -o2 1.88(2) 1.80(2) 02-r-o3 e70) e5(1) -03 1.90(2) 1.80(2) o3-r-o1 96(1) 97(21 Av. 1.863 1.797 Av. 96.7 97.3 S(se)-O4 1.45(2) 1.60(2) O4-S(SelO5 112(1) 114(1) -o5 1.46(21 1.56(2) o+s-o6 109(1) 107(1) -o6 1.5q2) 1.59(2) O/LS-O7 10q1) 108(1) -o7 1.58(2) 1.60(2) 05-s-o6 111(1) 11q1) Av. 1.505 1.588 05-s-o7 1oql) 109(1) 06-s-o7 108(1) 108(1) Av. 109.7 109.3 K1-O5[x 2] 2.84(2) 2.8q2) Mgl-06[x3] 1.9q2) 2.04(21 -O4[x2] 2.90(2) 2.8812) -O2[x3] 2.0e(21 2.13(21 -06[x2] 2.e342) 2.86(21 Mg2-O3[x3] 2.0421 2.04(2) -O4[x2] 3.06(2) 3.06(2) -O8[x3] 2.1412) 2.1042) M-OS[x3] 2.67(2) 2.80(21 M9+O1[x6] 2.11(2) 2.11(2) -O7[x3] 2.7q21 2.74(2) o&o2' 2.66(2) 2.7q3) -O1[x3] 2.76(21 2.82(21 -o7' 2.6q2) 2.7513) Na1-O4[x3] 2.36(2) 2.3312) -O8[x2] 2.79(31 2.7643) -o8[ x 3] 2.44(21 2.46{2) o2-oto7 110(2) 108(2) Na2-O5[x 6] 2.35(2) 2.37(21 'Probable H bond. 1008 KONNERT ET AL.: FUENZALIDAITE AND CARLOSRUIZITE and Mg2 coordination octahedra (see Fig. 2). They are to thank Mary E. Mrose for her early X-ray studies of fuenzalidaite crys- apparently strongly H bonded to 02 in the IO, group and tals. 07 in the SOn group (Table 8). Three HrO molecules Rrrnnoxcns crrED form a tight triangle in the a-b plane but are probably not bonded by H atoms. Ericksen, G.E. (l 993) Upper Tertiary and Quaternary continental saline in central Andes. In R.V. Kirkham, W.D. Sinclair, R.I. Fuenzalidaite and carlosruizite have structures that bear deposits the Thorpe, and J.M. Duke, Eds.,Mineral depositmodeling, in press.Geo- a distant resemblanceto those of the group. These logical Association of Canada, Ottawa. structures are rhombohedral or trigonal, with a axial Ericksen, G.E., Mrose, M.E., Marinenko, JW., and McGee, J.J. (1986) lengths of about 7 A, and contain layers consisting of Mineralogical studies of the nitrate deposits of Chile. V. Iquiqueite, sheetsof tetrahedral sulfate anions joined to an r6tAl(or NaoKrMg(CrOJB,O.,(OH) l2HrO, a new saline mineral. American I61Fe) Mineralogist, 7 l, 830-836. sheet,including OH groups, and the layers are sep- Hall, S.R., and Stewart, J.M., Eds. (1988) XTAL2.4 user'smanual. Uni- arated by K (or Na) ions. The minerals described here versities of Western Australia and Maryland. are the first of this type in which a layer of IO, groups Mandarino, J.A. (1976) The Gladstone-Dalerelationship. I. Derivation occurs. of new constants. C-anadian Mineralogist 14, 498-502. - (1981) The Gladstone-Dale relationship. IV. The compatibility The phase systemsin which these minerals form have concept and its application. Canadian Mineralogist, 19' 441-450. not been studied, and an attempt to obtain fuenzalidaite Mehrotra, B.N., Hahn, Th., Eysel,W., Rtipke, H., and Illguth, A. (197E) from a stoichiometric solution at room temperature was Crystal chemistry of compounds with thenardite (Na'SOoD structure. not successful. Neues Jahrbuch fiir Mineralogie Monatshefte, 408-421. Svensson,C., and SUhl, K. (1988)The crystal structureof NaIO, ar 298K. Acxxowln'ocurrrrs Journal of Solid State Chemistry, 77,112-116. We are grateful to Edward C. Chao of the U.S. Geological Survey for MrNuscmpr RrcErvEDAucusr 12, 1993 his measurement of the refractive indices of carlosruizite. We also wish MaNuscnrrr AccEP,rEDApnrl 14, 1994