American Mineralogist, Volume62, pages321-326, 1977

Liottite, a newmineral in the cancrinite-davynegroup

SrrpeNo Msr.r-rNoAND PAoLo ORlnNor Istiluto di Mineralogia e Petrografia, Uniuersitit di Pisa Via S. Maria 53,56100 Pisa (Italv )

Abstract

A new mineral, liottite, was found in Pitigliano (Tuscany, Italy). It occurs, as flattened hexagonalprisms up to I cm in diameter,inside cavities of ejectedblocks in a pumice deposit. ThespacegroupisP-6m2:a:12.842,c:16.09lA.Opticaldataco:1.530,r:1.528.The density is 2.56 g cm-3. The strongestlines in the powder patterns are 4.84(36),3.715(100), 3.3I 5(75),2.686( l0), 2.47l(10), 2:l4l(24), 1.801( 10). The chemicalformula (Caro.zoNae.zgKg.az Fef.3,u)(Si,.3{Alr?.",)O?2(SO4)3 ,r(COs),.,rCI, .1(OH)s 6s. l.83HrO, the hexagonalsymmetry, and the lattice dimensionsshow that liottite is a new member of the cancrinitegroup.

Introduction magma. The most common mineral assemblage, from Pitigliano (Tuscany,Italy) is a locality well known which is also characteristicof the specimen was is vesuvianite, to collectorsand studentsof minerals,because of the which the new species obtained, (grossular pyroxene,and, sub- occurrenceof a rich variety of well-crystallizedmin- garnet and andradite), erals.Within a program of reexaminationof Tuscan ordinately, melilite, latiumite, anorthite, and brandi- mineralogy, a study of the various mineral phasesof site. that locality was undertaken.The study was fruitful and physical properties becauseat least three different minerals of the can- Crystallographic crinite-davynegroup were found: one was identified Liottite is transparent and colorless.The crystals as afghanite and two appearedto be new mineral occur as well-developedflattened hexagonalprisms, specieson the basis of spacegroup and cell dimen- up to one centimeterin diameter, inside the cavities sions.The aim of the presentpaper is the description of the blocks. Measurementby two-circleoptical go- and discussionof one of thesenew minerals,which niometer indicated hexagonal symmetry. No evi- was named liottite in honor of Luciano Liotti, enthu- dencecontrary to dihexagonaldipyramidal symmetry siastand well-informed collector,who kindly gaveus was discovered in morphology; the various forms the material in which liottite was first found. were then indexed assuming6/mmm symmetry.The The new mineral and its name were approved by habit of the crystalsis illustrated in Figure l. Other the New Minerals ahd Mineral Names Commission minor forms appearing in the crystal on which we of LM.A. Type material is depositedin the museums made our goniometric measurementswere: {120}, of Instituto di Mineralogia e Petrografiadell' Univer- {121}, {l l2l, ll13}. They were not included in the sitd di Pisa (Italy) and Istituto di Mineralogia dell' drawing becauseof their minor development. Universitddi Modena (Italy). Weissenbergand precessionphotographs indicated Laue symmetry 6/mmm, with a = 12.9and c = l6.l Paragenesis A. As no systematicabsences were observed,possible The sample studied is one of numerous ejected spacegroups are P6/mmm, P6mm, P62m,P6m2, and blocks found in a pumice deposit,which is indicative P622. of the explosiveactivity of a small volcanic centerset The X-ray powder data (Table I ) were obtainedby up in the Pleistoceneon the rims of the great Laten means of a Phillips diffractometer, scanning speed caldera. These blocks are the product of a syntexis l/2" 20 per min, Ni-filtered Cu radiation (I : betweenthe carbonaterocks which make up the walls 1.54051A;. fne powder pattern was readily indexed of the vent of the magmatic reservoirand a trachytic using prominent reflectionson the single-crystalpho- 321 322 MERLINO AND ORLANDI: LIOTTITE. A NEW MINERAL

c:lool l n:llo 1l u:ltoal m:l lool o:llo2l r:lzosl a:l 11Ol n =ltosI e:lttrl

Flc. l. Drawing of a well-developed crystal of liottite. tographs.The cell parameters derived from single-cry weightpercentages was 100.0. The resultsof theanal- stal study and refined by a least-squaresmethod, ysesare givenin the first columnof Table2. usingthe indexedpowder data, are given in Table3. Refractiveindices, to : 1.530,e : 1.528,were mea- Relatedcomfounds and structuralconsiderations suredby a doublevariation method using o-nitrotol- The chemicaldata reportedin Table 2, together ueneas liquid. The densityof liottite,also reported with the hexagonalsymmetry and the cell parame- in Table 3, wasdetermined by suspensionin a mix- ters,clearly show a closerelationship with the miner- ture of bromoform and acetoneas 2.56 + 0.02 als of the cancrinite-vishnevite-davyneseries with g cm-'. The hardnessof the mineralis 5 in the Mohs chemicalcomposition (Na,Ca,K).-8AlsSi6O24 (COs, scale. SO1,CI,OH)1-r'1-sHrO.On this basisthe unit-cell contentsof liottitewere calculated assuming 36(Si + Chemicalcomposition Al) and are given in Table 2. From the excessof oxygenatoms over 72, a contentof 3.58hydroxyl The chemicalcomposition was obtained in the fol- anionscan be inferred;in fact, hydroxyl ions are lowingway: CaO,NarO, and KrO weredetermined presentin cancriniteminerals as indicatedby chem- by atomic absorptionspectrometry using a Perkin ical analysesand structuralstudies and were actually Elmer 303instrument. CO, and H2Owere obtained found in liottite by crystal-structuredetermination by the microdeterminationof carbonand hydrogen (Merlinoand Mellini, 1976).The followingchemical carriedout with the Carlo Erba elementalmicro- formula was thus calculatedfor liottite:(Ca,o.rrNar.2, analyzerll04 instrument.Cl and SO, were deter- Ka.ezF ef 1,.)(S i,8.sn A ltt..')Orr( S 04)a.r'( C Or)'.r,C l, ., mined by X-ray fluorescencespectrometry, using as (OH)r.url.83 HrO. Liottite containscalcium as its referencestandard samples of analyzedcancrinite to dominantcation, a relationwhich wasnot found in whichknown quantities of sulphurand chlorine were anymineral of thecancrinite group except one micro- added.Starting from the known quantitiesof the sommite,as shownin Figure2. other elements,SiOr, Alros, and FerO, were deter- The crystal structureof cancrinite,space group minedby X-ray fluorescencespectrometry according P6s,a : 12.75,c : 5.14 A, was determinedby to the method of Franzini and Leoni (1972), in- Pauling(1930) and refinedby Jarchow(1965). It is troducingthe appropriatecorrection factors for sul- madeup of six-foldrings of tetrahedra:each ring is phur and chlorineand assumingthat the sum of the linked to three ringsin the precedinglayer and to MERLINO AND ORLANDI: LIOTTITE, A NEW MINERAL 323

Tlsr-s l. X-ray powderdiffraction data for liottite

NK.L I /Io d obs d calc hkl IrIo d obs d calc o (A) (A) (A) (A)

100 2 L].L2 L1,. L2 +zz I r qcz ) 2 L.957 101 L I.L7 9.15 3o7I t 1.9s4 LO2* 1 6.52 6.52 406x 6 t-.932 1.930 oo3* 1 5 .37 513*l t.etz ( 3 L.872 ) 103* 36 4 .84 4. 83 z>t ) [ 1.869 2L0x 2 4.?L0 4.204 431 r. ett I <1 1.816 I 1l-3* 2 4.LL4 4.]-L6 2r8 J t r.815 21_Lx 2 4.07'./ 4.067 416x 10 1. BO1 1 .800 L04x 8 3.790 3.783 432 ) r.783 * I 300 100 3.7L5 3 .707 ""-t r.782 1 r.782 302* .2 e a?tr 3 .367 520*) I t.tat 213* 75 3.315 3.309 3o8 I r.768 nnc I 1 L,76a I 3.218 1oe [ 1.765 """ I 2 3 .21-7 J 2?O+) 3 .zTL 603x r L.753 r . / )1 105 1 3.095 3.O91 Aaa* 2 L.73L 303 1 3.O58 3.O50 2rg * 1 L .646 L.645 311x 3 3.O33 3.O29 613 tr 1 1.618 1-.6L7 3L2x 4 2.885 2. BBO 605'[ j r. ooo 6 1.606 205 I 2.7A5 440xJ I 1,.60s l 9 2.787 40O*j 2.7a4 531 i 1. s81 [ 223+ -^"1/vt <1 2 2.760 2.755 ( 1.581 I 1.581 40Lx 5 2 .7 45 2.740 328 ) L r. sao oo6 * 10 2.686 2.6A? 1 .55e | * l:: I I 1 qqq 313 7 2.678 2.674 )r. ( 1-. 559 402x 3 2.630 a.oa6 525 ) I r. sse 106

'Ortly the reflexions marked wlth a star were used for the refinement of the unlt ce11 dimensions. (zzo), (4oo), (403), (srs), (s20), (44o), (4o9), (446) were used because their lntensitles in the single crystal photographs were much greater than (oo5), (205), (116), (zz7), (432) and (33s), (605), (2110), (s43). three other rings in the succeedingone, in a three- The diffractionpattern of the specimenused by dimensional framework. The layers succeed each Jarchow(1965) to refinethe structureof cancrinite other along the c axis, according to the stacking showeddiffuse spots symmetrically disposed relative sequenceABAB... to the sharpones at I 3/7 c* in reciprocalspace MERLINO AND ORLANDI: LIOTTITE, A NEW MINERAL

Tnsr.r 2. Chemical data and unit-cell contents in uesof c parameterequal to 5c, 8c, llc, l6c, and2lc, liottite wherec = 5.13A. the diffraction patternsof all these cancrinitesdiffer as regardsthe much weaker diffuse wt.% cefl contents reflectionsbut do not differ in the positions and in- tensities of the sharp spots. This indicates, as the sio2 30.51 Si 18.34 authors remark, that they have the samealuminosili- A1^O 24.92 A1 ", L7.66 cate framework structure,differing only in the order- 3 Fe^O_ o.36 F'"t o.16 ing of the cationsoutside the framework, which leads CJ to the appearanceof the satellitereflections. CaO 16.71- Ca IO.76 Natural and syntheticcompounds exist which, al- Naro 7 .97 Na o ?o though structurally related to cancrinite,have a dif- nzo 4.98 K 3.A2 ferent aluminosilicate framework. Bariand et al. (1968)found and studiedafghanite, a new alumino- to3 8.66 =o4 3.91 silicate with unit-cell content (Na,Ca,K).u(Si,Al)48 CO, 2 .1_ Qos L.72 O,o2(Cl,SO.,CO')', l.8HrO. Chemicalcomposition C1 2 .57 C1 2 .61_ and crystallographic data, reported in Table 3,

1a 3.62 indicated afghanite as a member of the cancrinite "ro "ro group, with an 8-layer sequenceof six-membered o 73.79 rings. RecentlySieber and Meier (1974)prepared and 100 . 5B studied Losod, a compound with idealized formula -cl-o o. 58 NarrAl,rSi,rOos.l8HrO.Its celldata, also reported in Table 3, indicated it is a member of the cancrinite group with a 4-layersequence ABAC. 100 . oo Liottite is another member of this group. Cell data pointed to a 6-layer sequenceof six-memberedrings; this has been confirmed by a crystal structure deter- (satellite reflections), thus indicating some kind of mination (Merlino and Mellini, 1976),which has led superstructure.Foit et al. (1973) and Brown and to the space group P-6m2and indicated the stacking Cesbron (1973) studied "cancrinites" from different sequenceABABAC. The structure refinement is in sources,finding superstructurescharacterized by val- progress.

Teslr 3. Crystallographicdata of compounds in the cancrinitegroup

Davyne "Losod" Liottile Afghani te

Sourc e Bariand et Sieber and This paper Bariand el al ( 1968) Meaer ( 1974) (1e6s)

q^..a -r^,,^ P6g P6-/mmc P6m2 P6-,mmc,P6^mc J JO P62c

a(A) r,2.70(0.03) 12.906(O.OO3) 1 .BZ.(o.ooJ) r (o.o") c (A) 5.s3(o.o2) ro.541(o.oos) 16.091(o.oo5) 21.35(0.O4) -3) u _ (s.cm- 2.2r 2.6L 2.6': caac. -3) D (e'cm 2. t5 2 .56 2.55 meas. " z* 2 46 8

nunbeh, ad laqzn..t ctd rir-mernbe.tced zing.t in thz AQ,qLtertce. MERLINO AND ORLANDI: LIOTTITE, A NEW MINERAL 325

Ca+Sr

A

I o t o T ^l ro I o o o

+ a T +o + + Na K

Frc.2. Cationchemistryofliottite,comparedwiththatoftheothermineralsincancrinitegroup.ThedataarefromDeeretal.(1962) and Bariand et al. (1968),excluding the analyseswith cation sums lessthan 6 on the basisof l2 (Si + Al).

O Cancrinite CO3-dominant anion outside the framework * Vishnevite SO?-dominant anion outside the framework I Microsommite Cl- dominantanion outside the framework O Davyne Cl dominantanion outside the framework X Afghanite Cl dominantanion outside the framework A Liottite SO? dominantanion outside the framework

Acknowledgments Comparisonavec les min6rauxdu groupedela cancrinite.Bull. Thanks are due to Mr. R. Cioni and Dr. L. Leoni who made Soc.fr. Minbral Cristallogr.,9l, 34-42. respectively the absorption spectrometry and X-ray fluorescence Brown, W. L. and F. Cesbron(1973) Sur le surstructuresdes spectrometry analyses. Particularly helpful were the suggestions cancrinites.C.R. Acad. Sci.Paris, 276, SerieD, l-4. and comments by A. Kato. The financial support of Consiglio Deer,W. A., R. A. Howie and J. Zussmann(1962) Rock-forming Nazionale delle Ricerche, Roma, is also kindly acknowledged. Minerals,uol. 4, FrameworkSilicates. Longmans, London, Foit. F. F., D R. Peacorand E. W. Heinrich(1973) Cancrinite References with a new superstructurefrom Bancroft,Ontario. Can. Min- Bariand, P., F. Cesbron and R. Giraud (1968) Une nouvelle espdce eral..1 1.940-951. min6rale: I'afghanite de Sar-e-Sang,Badakhshan, Afghanistan. Franzini,M. and L. Leoni(1972) A full matrix correctionin X-ray 3?6 M.ERLINO AND ORLANDI: IJOTTITE, A NEW MINERAL

fluorescenceanalysis of rock samples.Mem. Sbc. ToscanaSci, Pauling, L. (1930)The structureof somesodium and caicium Nat., 79,7-22. aluminosilicates.Proc. Natl. Acad. Sci..16. 453-459. Jarchow, O, (1965) Atomanordnungund Strukturverfeinetung Sieber,W. and W. M, Meier (1974)Formation and propertiesof von Cancrinit.Z. Kristallogr.,122, 4M4n. Losod,a newsodium zeolite. Helu. Chim. Acta,57,1533-1549. Merlino, S, and M. Mellini (i975) Crystalstructures of cancrinite- '76. like rninerals.Zeolile An Internallotial Conferenceon lhe Occurtence,Properlies, and Utilization of Natural Zeolites. Pro- Manuscript receiued,April 9, 1976;accepted gram and Abstracts.Tucson, Arizona, p. 47. lor publication,September /,5, 1976.