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Re-Examination and Crystal Structure Analysis of Litidionite

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Re-Examination and Crystal Structure Analysis of Litidionite American M ineralogist, Volume60, pages471474, 1975 Re-examinationand Crystal StructureAnalysis of Litidionite Josr M. MenrrN Pozest, Grusrppr Rossr, eNn Vrrronto Tp.zzott C.N.R., Centro di Studio per la Cristallografia Strutturale, Istituto di Mineralogia, uia Bassi 16, 27100 Pauia, Italy Abstract Litidionite,CuNaKSi.Oro, occurs with tridymitein lapilli stronglymodilied by fumarolic activity in the Vesuviuscrater. It is triclinic, spacegroup Pi; the latticeparameters are: d = 9.80(1)b=8.01(l),c:6.97(t)A,o=l14.l2(8)',P=99.52(6)',r:105.59(8)",2:2.lts crystalstructure-determined by Pattersonand Fourier methods,using single crystal diffrac- tometerX-ray data,and refinedto an R indexof 0.032for 1450reflections with F" ) oFo-is the sameas for fenaksite,FeNaKSi.O,o. Tubular chains of silicatetrahedra, formed by the condensationof vlasovite-typechains, are interconnected by copperand sodium atoms which havea five-foldpyramidal coordination. Potassium atoms occur in the largecavities within the chains. Introduction well-formedaugite crystalsejected by the volcano. The name litidionitewas given by E. Scacchiin The fumarolicaction coated the nucleiwith a layerof 1880(Zambonini, 1935) to very tiny blue crystals white microcrystallinetridymite (considered as opal associatedwith glassof thesame color in lapillifound by Zambonini) which is overlaid by a blue glassy in the Vesuviuscrater. Zambonini (1935) had difficul- crust whose cavities are coated by litidionite, ty measuringthe interfacialangles of litidioniteand tridymite,and minor wollastonite.Litidionite is the could only concludeit to be triclinicor monoclinic unique copper mineral occurring in these lapilli, sphenoidal.He alsodetermined 2V, : 56o,and in- although severalother copper minerals(covellite, cyanochroite,chalcocyanite, dicesap : 1.548,0o : 1.574.The chemical analysis tenorite,chlorothionite, he carried out, which yielded the formula (K, and others)were produced by the fumarolicactivity Na)rCu(SirOr)r,is very doubtful owing to the difficul- in the Vesuviuscrater. ty in obtainingpure litidionite. X-Ray Crystallography No further data or publicationappeared on this mineral other than an unindexedpowder pattern The latticeparameters of litidionite(Table l) were pw (Jceoscard No. l8-713).In thetext bookslitidionite measuredwith a Philips I100computer-controlled powder pattern, is consideredas an inadequatelycharacterized and diffractometer.Its X-ray obtained pw doubtful species.Accordingly we havere-examined with a Philips 1050diffractometer using CuKa litidionite and determinedits crystal structure. radiationand NaF asinternal standard, is compared Materialused in thisstudy was provided by Professor in Table2 with the data on the Jcposcard No. 18- : Carobbi from specimensthat had been previously 713.The threestrong lines of the Jcpns data-d :3.82 studiedby himselfand Zambonini. 4.31,d: 4.10,and d A-correspondto the threestrongest lines of tridymite(Jceos card No. l8- Occurrence I 170). Litidioniteoccurs as tiny platesin lapilli strongly The powder pattern and the lattice parametersof modifiedby the fumarolicactivity subsequent to the litidionite are very close to those of fenaksite, Vesuviuseruption of 1873.The dimensionof the FeNaKSirOro(Golovachev et al, l97l). lapilli rangefrom a few millimetersup to 25-30mm. ChemicalFormula Thenuclei of thelapilli are small fragments of rock or Carobbi (Zambonini, 1935) carried out one I Present address: Depto. de Cristalografia y Mineralogia, chemicalanalysis of litidioniteand gave the tentative Facultad de Ciencias, Universidad de Madrid, Spain. formulaNarKrCuSirOz. Zambonini (1935) considers 471 MARTIN POZAS, ROSSI, AND TAZZOLI Tlslr l. Unit Cell Data of Litidionite and Fenaksite Tlals 3. Atomic Coordinates* and Equivalent lsotropic Temperature Factors** litidionire fenaks i te a 9.80(1) A lo.o0 A Atom xla vlb z/c B,,(A-) b 8.01 " 8.18 c 6,97 " 6.98 Cu o.4122(r) 0.r287(r) o.1624(r) o.74 o 114.12"(8) rL4.7" si (1) 0.8593(1) o.71 42(2) o.8119(2) o.65 B 99,s2" (6) 100.7" si (2) o.1 222 (r) o.3545 (2) o.5664(2) o.66 Y 1os.s9'(8) 105 .0" si (3) 0.2110(I) o.287 7 (2) o.9s82(2) o,59 (4) Chemical fornula CuNaKSi,0, ^ FeNaKSi, 0. ^ si o.7256 (r) o .3825(2) o.7s57(2) o.68 4 tu 4 tu Space group P1 P1 o(1) 0.s682 (3) o.2o72(4) o.0323(4) 1.25 z 2 2 o(2) o.27 16 (3) 0.1161(4) 0.9166(s) l.04 0(3) o. 8535(3) o.3320(4) o.o452(5) D. L.22 z. t) o(4) 0.o3o2(3) 0.18s1(4) o.8549(5) -ca1c.noDs. r.64 2.85 o(s) o .252r(3) o.0432(4) o.2803(5) 1.34 o(6) 0.7943(3) o .4314(4) o.4ro2(4) r.20 o(7) o.s561(3) o.2077(4) o.4459(5) The unit ce11 parameters given by Golovachev et al, did 1.30 0(8) o.2s62(4) o.447r(5) not correspond to the reduced cell and were tianl?orned 0.215s(5) r.76 0(9) o.8331(3) o.2s35(4) to those given in this Table through the following mtrix 0.6323(s) 1.30 (o11/TT0/1oo). o( r0) o.2716(3) o.4o72(4) o.8286(s) 1.61 0.oo38(r) 0.2033(r) 0.3348(2) l.58 Na o.4090(2) 0.1295(3) o. 6633(4 ) 7.57 the analysisas very doubtful owing to thedifficulty in a With standard deoiations in parentheses separatingthe mineral from associatedtridymite and a* After Hamilton (1959). blueglass. In effect,if it is assumed,on th; basisof the closeresemblance of the crystallographicdata, that litidionite and fenaksiteare isostructural,the formula should be CuNaKSi4Olo.A chemical for- mula very closeto this can be obtained from Carob- Tlslr 2. X-ray Powder Data of Litidionite bi's analysis if we assumethat the material analyzed contained about 40 percent tridymite. JCPDS18-713 The crystal structure analysis fully confirms that dob". dcalc, hkl Tnnlr 4. Analysis of the Anisotropic Thermal 6,75 6.76 110 6,73 50 Parameters in Litidionite* 6.08 l0 5,16 10 4.485 4.483 200 r.m. s. Uia U.b U.c Atom U.a U.b U.c 4.37 60 trid. 4,lo ou Erld. o.084(1 ) 64 51 t55 0(s) 0.103 (6) 128 125 50 4.046 4,O48 15 0.089(1) 38 106 67 o.129(5) 11I 54 60 0.114(r) 64 145 100 0. 154(s ) 134 54 126 3.82 40 trid. o.073(3) 3.6s2 3.664 2Il 18 160 92 63 o.082(7 ) 90 63 171 3.66 10 0.091(2) 7I \27 3.372 3.379 29 0.112(6) 46 6s 96 220 r00 3.36 I00 0. 105( 2) 82 143 100 0. 163(5) t37 38 84 3.223 3.226 2to 75 3.22 OU o.067(3) 80 65 178 o. o98(6 3.046 ) I33 118 46 3.o42 tL2 10 0.o90(3) 85 31 88 0.107 (6) 64 99 44 1 ^o, ,3.033 111 0.112 (2) 169 65 91 0.169 (5 ) 53 151 9I 10 3.04 \: .ozo oo2 o.o78(3) r23 62 53 0(8) o.1o0(7) 81 95 149 (2.e71 311 0.086(3) 97 29 t43 0.134(6) 1I3 10 118 0.095(2) 146 91 94 o.197 (5) 2.976 <2.976 2L2 13 2.95 60 155 98 77 202 0. 064(3) 75 58 168 0(9) 0.087(7) 85 56 170 lz.stt o.o93(3) 2.835 2,840 r20 18 76 52 18 o.724(6) 35 134 99 2.82 30 o.1 13 (2) 170 54 92 0.162(s) r24 IIl 94 2.675 2.672 311 37 z.o) 30 o.o93(7) lo7 86 141 o(10) 0.084( 2,567 2.563 302 7) 87 164 53 13 o.1o9(6) 51 56 r29 o.12r(6) 44 tO6 132 2.460 2.451 032 7 o.165(s) 136 34 90 o.r99 (s) 133 89 115 2.409 2,473 230 85 2,40 80 0(2) 0.085(7) )t l)J nt 0.1.L2(2) 95 147 87 2.23 10 o.119(s) 103 85 29 o.r49(2) 27 96 126 1.980 r.982 r22 10 o.134 (5 ) 138 115 73 o.160(2) 117 5a 144 L924 L.920 o42 l0 0. ro5(5) 99 123 t\2 0.109(3) 55 78 155 0.121 (6) 40 78 (3) r.916 1.919 510 lo I 01 10 138 o.135 52 18 72 0.144(s) 52 t45 56 o.112(3) 57 t62 73 1.84 lo 0.079(8) 342 5 163 14 96 1.80 t0 0.118(6) 97 30 88 0.205(5) 75 65 \74 r Root mean square lhermal vibratiotrs along the ellipsoid (i) The unit cel1 parameters given axes ana in Table 1 were used angles (o) belween !he crystallographic ixes and cire principal axes for indexing (Uj) of the vibration ellipsoid. CRYSTAL STRUCTURE OF LITIDIONITE 4't3 TnsLe5. InteratomicDistances and Principal out in the manner describedby Davies and BondAngles in Litidionite* Gatehouse(1973) to yield valuesof F" and oF". The intensitiesof 2677 independentreflections Di st aoce s AEOhS Angl e s weremeasured; of these1450 have Fo ) oFo and were used in subsequentcalculations. Three standard si(1) - o(3) r.623L o(3)- si(1) - o(4) l06.o" o(4) r.623 o(5) 114.6 reflections, monitorized at three-hour intervals, o(s) t.572 o(9) r08.4 5 per- 0(9) r .633 o(4) - si(1) - o(s) 110,6 showedno variation in intensitygreater than o(9) 105.4 No absorptionnor extinctioncorrections were r .613 o(s)-si(r)-0(9) I11.3 cent.
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