Introduction

Holmquistite belongs to Mg-Fe-Mn-Li amphibolegroup and has BLi gt 10 atoms per formula unit (apfu) andBNa lt 05 apfu (Leake et al 1997) It occurs at or close tothe contact between lithium-rich pegmatites and countryrocks (eg Deer et al 1999 London 1986) Holmquistiteclose to the end-member composition may occur in bothorthorhombic (Pnma Whittaker 1969 Irusteta ampWhittaker 1975 Litvin et al 1973) and monoclinic(P21m Ginzburg 1965) space forms Sodian fluoroclino-holmquistite sodic ferri-clinoferroholmquistite and ferri-clinoferroholmquistite with C2m symmetry were reportedby Litvin amp Petrunina (1975) Caballero et al (1998) andOberti et al (2003) respectively In the Fe-Mg-Mn-Liamphiboles several symmetries are possible due mainlydue to (local) stereo-chemical reasons related to the size ofthe B-group cations the role of temperature and pressure

of formation is also relevant and is currently the object ofmuch work End-member anthophyllite is orthorhombicbut small amounts of Fe andor Mn at the B-site inducemonoclinic (P21m or C2m) symmetry The space groupP21m occurs for Mg-rich compositions in the systemcummingtonitendashmanganocummingtonitendashgrunerite[ideally A BMg2

CMg5TSi8 O22 (OH)2 A BMn2

CMg5TSi8 O22 (OH)2 and A BFe2

CFe5TSi8 O22 (OH)2 respec-

tively] (Hirschmann et al 1994 and Yang amp Hirschmann1995) Yang et al (1998) and Boffa Ballaran et al (20002001) have characterized and thermodynamic modelled theP21mndashC2m transition as a function of composition (BXFe)pressure and temperature on the cummingtonite-gruneritejoin

Relations between the space-group symmetry andchemical composition in BLi amphiboles are not yetcompletely understood Moreover amphiboles ofholmquistitic composition have never been synthesized

Eur J Mineral2003 15 321-327

Dedicated to the memoryof Luciano Ungaretti

Synthesis and characterisation of ferri-clinoferroholmquistiteLi2(Fe2+

3 Fe3+2 )Si8O22(OH)2

GIANLUCA IEZZI1 GIANCARLO DELLA VENTURA2 GIUSEPPE PEDRAZZI3 JEAN-LOUIS ROBERT1

and ROBERTA OBERTI4

1ISTO-CNRS 1A Rue de la Feacuterollerie F-45071 Orleacuteans Cedex 2 France2Dipartimento di Scienze della Terra Universitagrave della Calabria Arcavacata di Rende I-87036 Italy

3Dipartimento di Sanitagrave Pubblica Sezione di Fisica INFM Universitagrave di Parma Via Volturno 39 I-43100 Parma Italy4CNR-Istituto di Geoscienze e Georisorse sezione di Pavia via Ferrata 1 I-27100 Pavia Italy

Abstract This work reports the synthesis and crystal-chemistry of ferri-clinoferroholmquistite in the system Li2O ndash FeO ndash Fe2O3ndash SiO2 ndash H2O Ferri-clinoferroholmquistite has a very restricted temperature stability An almost monophase amphibole productis obtained at 500degC for a wide pressure range (1-7 kbar) whereas a Li-bearing pyroxene becomes predominant for T sup3 600degCThe X-ray powder pattern of ferri-clinoferroholmquistite was indexed in the C2m space group Refined cell dimensions are a =9489 (2) b = 18036 (7) c = 5313 (3) Aring b = 10159 (3)deg Infrared spectra in the OH-stretching region show the presence of asingle and very sharp band at 3614 cm-1 which is assigned to the Fe2+Fe2+Fe2+ trimer at the OH-coordinated M1M1M3 octahedraand a small satellite band at 3644 cm-1 which was assigned to Li at M3 Moumlssbauer spectra can be fitted to three doublets assignedto Fe3+ at M2 Fe2+ at M1 and Fe2+ at M3 respectively with a calculated Fe3+Fe2+ ratio of 23 suggesting a composition close tothe nominal one The spectroscopic data show that synthetic ferri-clinoferroholmquistite has a strongly ordered cation distribu-tion in agreement with single-crystal refinements done by Caballero et al (1998) and Oberti et al (2000) on natural samples withrelated Li-rich compositions

Key-words synthesis amphiboles lithium cell-parameters Moumlssbauer spectroscopy infrared spectroscopy short-rangeordering

0935-1221030015-0321 $ 315copy 2003 E Schweizerbartrsquosche Verlagsbuchhandlung D-70176 StuttgartDOI 1011270935-122120030015-0321

Presently at Dipartimento di Scienze della Terra Universitagrave ldquoG DrsquoAnnunziordquo I-66013 Chieti Scalo Italye-mail dellavenuniroma3it

G Iezzi G Della Ventura G Pedrazzi J-L Robert R Oberti

and little is known about their stability In this paper wedescribe the synthesis and crystal-chemical characteriza-tion of end-member ferri-clinoferroholmquistite

Experimental methods

Starting materials were prepared both as silicate gelsaccording to the method of Hamilton amp Henderson (1968)and as hydroxide-oxides mixtures Iron was introduced inthe gel both as trivalent and as metallic Fe following theprocedure of Monier amp Robert (1986) Hydrothermalsynthesis was done in the T range 500-800degC and in theP(H2O) range 1-7 kbar for a maximum duration of 12 daysThe syntheses were done in two different internally-heatedpressure vessels one for runs below 4 kbar and the otherfor higher P values T was monitored by three mantled-type-K thermocouples (accuracy plusmn 5degC calibrated againstthe melting point of NaCl at 1 atm) and disposed aroundthe hot-spot P was recorded by a transducer (accuracyplusmn 20 bars DallrsquoAgnol et al 1999) In the runs atP pound 4 kbar fO2 conditions were imposed by a H2-Ar gasmixture and fH2 was monitored by a Shaw membrane(Gaillard et al 2001 and references therein) In the runs atP sup3 4 kbar pure Ar was used as the pressure medium thusbuffering the system at NNO+3 (Schmidt et al 1997) The500degC runs were internally buffered due to the low perme-ability to hydrogen of the gold capsule Because the perme-ability to hydrogen of gold is three orders of magnitudelower than that of silver and platinum (Chou 1987) wecompared experiments done under the same P T X condi-tions using both gold or Ag60Pd40 capsules The experimentdone in the gold capsule produced monophase amphibolewhereas that done in Ag60Pd40 gave an assemblage of Li-pyroxene hematite and quartz This evidence confirms thatthe use of gold capsules precludes osmotic equilibrium at500degC for run times of the order of a few weeks

Step-scan X-ray powder patterns were collected at theUniversity of Roma Tre on a Scintag X1 diffractometeroperated in the vertical q-q configuration with Ni-filteredCuKa radiation and a Si(Li) solid-state detector Celldimensions were refined by whole-powder-pattern refine-

ment (Rietveld method) using DBW32 (Wiles amp Young1981)

Room-temperature FTIR spectra in the OH-stretchingregion (4000-3000 cm-1) were collected at the University ofRoma Tre on a Nicolet 760 spectrophotometer equippedwith a DTGS detector and a KBr beamsplitter The nominalresolution is 2 cm-1 spectra are the average of 64 scansSamples were prepared for FTIR spectroscopy as KBrpellets using the procedure of Robert et al (1989a)

For Moumlssbauer data collection samples were powderedin an agate mortar mixed with vaseline gel and placed in aplexiglass sample-holder This method limits preferentialorientation and texture effects The absorber thickness wasestimated on the basis of the mass absorption coefficientsfor 144 keV gamma radiation (Long et al 1983 Rancourtet al 1993) When necessary thickness effects were takeninto account (Lang 1963 Rancourt 1989 Pedrazzi et al1999 and references therein) Spectra were recorded intransmission mode at 297 K with a conventional constant-acceleration Moumlssbauer spectrometer The source was57CoRh with an activity of about 370 MBq (10 mCi)Calibration was done using either a-Fe foil or an SNPabsorber at room temperature Isomer shift are expressedrelative to a-Fe

Results and interpretation of the data

Experimental products

Run powders were studied by optical microscopypowder XRD and SEM Syntheses done at 500degC and pres-sures up to 7 kbar gave an essentially monophase amphi-

322

Fig 1 SEM images of synthetic ferri-clinoferroholmquistite The crystals have an average width of 05 mm and lengths of up 10 mm Noother phases are detectable The scale bar is 2 mm (for both images)

Table 1 Run conditions for synthetic end-member ferri-clinoferro-holmquistite Sample Temperature

bole (plus negligible amounts of quartz) at higher T(sup3 600degC) amphibole is replaced by lithian clinopyroxene(dominant) + magnetite + quartz Amphibole crystals areacicular 05 5 mm on average (Fig 1) Both gels andoxide mixtures gave similar run products but the crystaldimensions obtained from gels are half those obtained fromoxides

X-ray diffraction

The X-ray powder patterns of three samples (101 207and 364 Table 1) were indexed in C2m refined unit-celldimensions are given in Table 2 The unit-cell edges arelonger and the b angle is smaller than the values reportedby Caballero et al (1998) for sodic ferri-clinoferro-holmquistite and by Oberti et al (2003) for ferri-clinofer-roholmquistite with some deviation from idealstoichiometry (namely some Na at M4 Mg at M1 and M3and Li at M3) Differences in the b value can be explainedby the M4Li content and those in the b value by the Mgcontent of the natural samples

Moumlssbauer spectroscopy

The Moumlssbauer spectra of samples 101 207 and 364 arealmost identical the spectrum of sample 101 is shown inFig 2 Refined Moumlssbauer parameters (Table 3) varywithin experimental error for the three samples Threequadrupole doublets were resolved of which two are due toFe2+ (around 22 and 28 mms) and one to Fe3+(03mms)Following Law amp Whittaker (1981) and Hawthorne (1983)the doublet with the largest quadrupole splitting wasassigned to Fe2+ at the M1 site whereas the other wasassigned to Fe2+ at the M3 site (Fig 2) The Fe3+ compo-nent was assigned to the M2 site (Fig 2) The Fe2+ Fe3+

ratio calculated from band areas is close to 32 for all threesamples

FTIR spectroscopy

The infrared spectra in the OH-stretching region fordifferent ferri-clinoferroholmquistite samples obtainedunder different pressure conditions are given in Fig 3They all show one very sharp (full-width-at-half-maximun-height FWHM = 4-5 cm-1) absorption band centred at3614 cm-1 and one minor satellite band at 3644 cm-1 Thepresence of a single band in the OH-spectrum of an amphi-

Synthetic ferri-clinoferroholmquistite 323

Fig 2 The Moumlssbauer spectrum of ferri-clinoferroholmquistite 101

Table 2 Unit-cell parameters for synthetic ferro-clinoferriholmquistite

Table 3 Moumlssbauer parameters for synthetic ferri-clinoferroholmquistite

G Iezzi G Della Ventura G Pedrazzi J-L Robert R Oberti

bole implies the presence of a single cation at the OH-coordinated M1M1M3 octahedra (eg Della Ventura1992) In addition the frequency value (3614 cm-1) iscompatible with the vibration of an O-H bond pointingtoward an empty A-site (Della Ventura 1992 Hawthorne etal 1997) Considering the above arguments and the cationdistribution derived by Moumlssbauer spectroscopy the mainband at 3614 cm-1 is assigned to the Fe2+Fe2+Fe2+-[A] -OHconfiguration From the work of Robert et al (1989b) onsynthetic lepidolites we know that the presence of Li at theoctahedral sites in micas which are closely related toamphiboles induces a +30 cm-1 wavenumber shift of theOH-band The 3644 cm-1 minor absorption is shiftedexactly 30 cm-1 toward higher frequencies with respect tothe main band at 3614 cm-1 therefore it can be assigned tothe Fe2+Fe2+Li-OH-A configuration it shows the pres-ence of a small (but significant) amount of Li at the NNtrimer of octahedra in the first coordination shell aroundthe anion site

The crystal-chemical formula of synthetic ferri-clinoferroholmquistite

The syntheses reported in this work did not providecrystals of a size suitable for X-ray single-crystal refine-ment andor SIMS analysis However the composition ofthe system is constrained to Si Fe Li H and O and theavailable crystal-chemical knowledge combined with FTIRand Moumlssbauer data allowed us to obtain the cation distri-bution Si is the only tetrahedral cation because Fe3+ isconsidered to be exclusively a C-group cation in amphibole(Hawthorne 1983) Moumlssbauer spectra confirm that Fe3+

occurs only in octahedral coordination and allow assign-

ment to the M2 site Moumlssbauer analysis also precludes thepresence of significant Fe2+ at the M4 site and indicatesordering of Fe2+ at the M1 and M3 sites Previous literaturesuggests that Li can be incorporated both at the M4 and atthe M3 sites Low Li contents were also reported at the Asite in a synthetic orthoamphibole (Maresch amp Langer1976) In the samples of this work FTIR analysis showsthat the A-site is empty and that the amount of octahedralLi is very low Thus the chemical formula of ferri-clinofer-roholmquistites synthesized in this work isA B(Li2-x Fe2+

x)C(M1M3Fe2+3-x

M2Fe3+2

M3Lix)TSi8O22(OH)2where the only departure from nominal stoichiometryshown by infrared is an almost negligible amount of Li atM3 (ie x ~ 0) which is locally balanced by Fe3+ at M2(Hawthorne et al 1993) in order to maintain electroneu-trality there must be an equal amount of Fe2+ at M4 whichis too low to be detected by Moumlssbauer spectroscopy Theseconclusions for a simple chemical system are in agreementwith those for the more complex natural samples (Oberti etal 2003)

Ordering of cations in syntheticferri-clinoferroholmquistite

Considerable efforts have been devoted in the lastdecade to characterizing short-range order in amphibolesby infrared spectroscopy (eg Della Ventura et al1996a 1996b 1999 Hawthorne et al 1996a 1996b

324

Fig 3 Infrared spectra in the OH-stretching region ofLi2(Fe2+

3Fe3+2)Si8O22(OH)2 Syntheses were done at 500degC and

variable pressure

Fig 4 The IR OH-stretching spectrum of ferri-clinoferro-holmquistite (a) compared to that of tremolite (b) Cumm =cummingtonite component (Mg at M4)

2000) The FTIR OH-spectrum of ferri-clinoferro-holmquistite (Fig 4a) albeit extremely simple can beused to derive useful information based on band multi-plicity and band widths

It is well known that the presence of two cations at theoctahedral sites directly bonded to the hydroxyl groupgives rise to four bands in the infrared OH-stretchingregion which can be assigned to the four possible config-urations (Strens 1966 Hawthorne et al 1996b DellaVentura 1992) The presence of a single band in the spec-trum of ferri-clinoferroholmquistite indicates that there isa single cation at the M1 and M3 sites which in turnimplies ordering of Fe3+ at the M2 site which is not coor-dinated to OH This result is in accord with the X-raysingle-crystal work of Caballero et al (1998) and Obertiet al (2000 2003) which shows that Fe3+ is stronglyordered at the M2 site in all Li-rich amphiboles so farrefined The small band at 3644 cm-1 also conf irms thatoctahedral Li is ordered at either the M1 or the M3 sitesin agreement with all structure refinements done onnatural samples from Pedriza (Caballero et al 1998Oberti et al 2000 2003) or on Li-bearing sodic amphi-boles (Hawthorne et al 1993 1994) which indicate thatCLi is ordered at M3

The presence of different cations at the sites involvedin the absorption is known to give rise to signif icant bandbroadening (ldquosubstitutional broadeningrdquo Strens 1974)Again the spectrum of ferri-clinoferroholmquistite hasvery sharp bands this situation has been found so faronly in tremolite (Fig 4) which is a strongly orderedamphibole (Hawthorne 1997) with an empty A site M4occupied by Ca (plus minor Mg Hawthorne et al 2000and references therein) and the three octahedral sitesoccupied by Mg The local cummingtonite environmentin tremolite gives rise to a well-defined component in thespectrum at 3668 cm-1 (arrowed in Fig 4) Cationdisorder at sites not directly bonded to OH such as thepresence of a cation at the A-site or the Na-Ca disorder atthe NNN M4 site strongly affects the OH-stretchingband width (Hawthorne et al 1997) The very sharpFWHM of the single main band in the spectrum of ferri-clinoferroholmquistite is therefore indicative ofextremely low amounts of Fe2+ at M4 and consequentlyof Li at M3

The local configuration around the OH-group in ferri-clinoferroholmquistite is identical to that in ferroactinoliteie FeFeFe-OH-A -SiSi (notation introduced by DellaVentura et al 1999) On the other hand the wavenumberof this band in ferri-clinoferroholmquistite is 10 cm-1 lowerthan in ferro-actinolite (Fig 5) Changes in cation occu-pancy at the NNN M2 site may also give rise to band split-ting and shift (Della Ventura et al 1999) For example inpargasites and Al-bearing tremolites there is a downwardshift of ~ 20 cm-1 due to the presence of Al at the M2 site(Hawthorne et al 2000) We tentatively attribute the down-ward shift of 10 cm-1 observed in ferri-clinoferroholmquis-tite relative to ferro-actinolite to the NNN effect of Fe3+ atthe M2 site However this point needs further experimentalsupport as cation disorder at M4 can also induce a similarshift

Conclusions

Ferri-clinoferroholmquistite Li2(Fe2+3Fe3+

2)Si8O22(OH)2 has been obtained in a very limited temperaturerange between 500-600degC for a wide pressure range(1-7 kbar) For T sup3 600degC it is replaced by an assemblageof pyroxene + magnetite + quartz These results confirmthe prediction based on petrological observation of Obertiet al (2003) on the upper thermal stability of this type ofLi-rich amphiboles Spectroscopic data show that ferri-clinoferroholmquistite has a strongly ordered cationarrangement in agreement with the prediction ofHawthorne (1997) on local bond-valence ground and withsingle-crystal refinements on Li-rich amphiboles (egCaballero et al 1998 Oberti et al 2000 2003)Moumlssbauer and infrared spectroscopy can be extremelyuseful in characterizing both long-range and short-rangeorder in synthetic phases which cannot be adequately char-acterised by EMP analysis and X-ray structure refinement

Acknowledgements We thank Bruno Di Sabatino forconstructive comments at the beginning of the workAnnibale Mottana and Ciriaco Giampaolo allowed us useof the analytical facilities at the University of Roma TreThanks are due to Sergio Lomastro for assistance in X-ray data collection and to Arnaud Papin Jacques Rouxand Bruno Scaillet for technical assistance duringsynthesis Part of this work was done during the stay of

Synthetic ferri-clinoferroholmquistite 325

Fig 5 The IR OH-stretching spectrum of ferri-clinoferro-holmquistite compared to that of ferro-actinolite (sample MH13Della Ventura unpublished)

G Iezzi G Della Ventura G Pedrazzi J-L Robert R Oberti

GI at ISTO-CNRS (Orleacuteans) financed by theUniversity of Chieti and an EGIDE-Italian ForeignAffairs Ministry fellowships The constructive criticismof referees Walter Maresch and Frank C Hawthorne isalso acknowledged

References

Boffa Ballaran T Angel RJ Carpenter MA (2000) High pres-sure transformation behaviour of the cummingtonite-gruneritesolid-solution Eur J Mineral 12 1195-1213

Boffa Ballaran T Carpenter MA Domeneghetti MC (2001)Phase transition and thermodynamic mixing behaviour of thecummingtonite-grunerite solid-solution Phys ChemMinerals 28 87-101

Caballero J-M Monge A La Iglesia A Tornos F (1998) Ferri-clinoholmquistite Li2(Fe2+Mg)Fe3+

2Si8O22(OH)2 a new BLiclinoamphibole from the Pedriza Massif Sierra deGuadarrama Spanish Central System Am Mineral 83 167-171

Chou IM (1987) Oxygen buffer and hydrogen sensor techniqueat elevated pressures and temperatures In ldquoHydrothermalexperiments techniquesrdquo (HL Barnes amp GC Ulmer eds)Wiley New York

DallrsquoAgnol R Scaillet B Pichavant M (1999) An experimentalstudy of a lower Proterozoic A-type granite from the EasternAmazonian Craton Brazil J Petrol 40 1673-1698

Deer WA Howie RA Zussman J (1999) Rock formingminerals Double-chain Silicates Ed Longman Scientific ampTechnical pp 692

Della Ventura G (1992) Recent developments in the synthesis andcharacterization of amphiboles Synthesis and crystal-chem-istry of richterites Trends in Mineralogy 1 153-192

Della Ventura G Robert JL Hawthorne FC (1996a) Infraredspectroscopy of synthetic (NiMgCo)-potassium-richterite InldquoMineral Spectroscopy a tribute to Roger G Burnsrdquo (MDDyar C McCammon and MW Schaefer eds) The Geoche-mical Society Special Publication 5 55-63

Della Ventura G Robert J-L Hawthorne FC Prost R (1996b)Short-range disorder of Si and Ti in the tetrahedral double-chain unit of synthetic Ti-bearing potassium-richterite AmMineral 81 56-60

Della Ventura G Hawthorne FC Robert J-L Delbove FWelch MD Raudsepp M (1999) Short-range order ofcations in synthetic amphiboles along the richterite - pargasitejoin Eur J Mineral 11 79-94

Gaillard F Scaillet B Pichavant M Beacuteny JM (2001) Theeffect of water and fO2 on the ferric-ferrous ratio of silicicmelts Chem Geol 174 255-273

Ginzburg IV (1965) Holmquistite and its structural variant-clino-holmquistite Trudy Min Muz Akad Nauk USSR 16 73-89 (inRussian)

Hamilton DL amp Henderson CMB (1968) The preparation ofsilicate compositions by a gelling method Mineral Mag 36832ndash838

Hawthorne FC (1983) The crystal chemistry of the amphibolesCan Mineral 21 174-481

mdash (1997) Short-range order in amphiboles a bond-valenceapproach Can Mineral 35 201-216

Hawthorne FC Ungaretti L Oberti R Bottazzi P (1993) LiAn important component in igneous alkali amphiboles AmMineral 78 733-745

Hawthorne FC Ungaretti L Oberti R Cannillo E (1994) Themechanism of Li incorporation in amphiboles Am Mineral79 443-451

Hawthorne FC Della Ventura G Robert J-L (1996a) Short-range order of (NaK) and Al in tremolite An infrared studyAm Mineral 81 782-784

Hawthorne FC Della Ventura G Robert J-L (1996b) Short-range order and long-range order in amphiboles A model forthe interpretation of infrared spectra in the principal OH-stretching region In ldquoMineral Spectroscopy a tribute to RogerG Burnsrdquo (MD Dyar C McCammon and MW Schaefereds) The Geochemical Society Special Publication 5 49-54

Hawthorne FC Della Ventura G Robert J-L Welch MDRaudsepp M Jenkins DM (1997) A Rietveld and infraredstudy of synthetic amphiboles along the potassium-richterite -tremolite join Am Mineral 82 708-716

Hawthorne FC Welch MD Della Ventura G Shuangxi LiuRobert J-L Jenkins DM (2000) Short-range order insynthetic aluminous tremolites an infrared and triple-quantumMAS NMR study Am Mineral 85 1716-1724

Hirschmann M Evans BW Yang H (1994) Composition andtemperature dependence of Fe-Mg ordering in cummingtonite-grunerite as determined by X-ray diffraction Am Mineral 79862-877

Irusteta MC amp Whittaker EJW (1975) A three dimensionalrefinement of the structure of holmquistite Acta Cryst B31145-150

Lang G (1963) Interpretation of experimental Moumlssbauer spec-trum areas Nucl Inst and Meth 24 425- 428

Law AD amp Whittaker EJ (1981) Studies of the orthoamphiboles1 ndash The Moumlssbauer and infrared spectra of holmquistite BullMineacuteral 104 381-386

Leake BE Woolley AR Arps CES BirchWD Gilbert MCGrice JD Hawthorne FC Kato A Kisch HJ KrivovichevVG Linthout K Laird J Mandarino JA Maresch WVNickel EH Rock NMS Schumacher JC Smith DCUngaretti L Whittacker EJW Youzhi G (1997)Nomenclature of amphiboles Report of the subcommitte onamphiboles of the International Mineralogical Associationcommission on new minerals and minerals name Eur JMineral 9 623-651

Litvin AL amp Petrunina AA (1975) On the crystal structure ofclinoholmquistite Konst Svoistva Mineral 8 6-8 (in Russian)

Litvin AL Ginzburg IV Egorova LN Ostapenko SS (1973)On the crystal structure of holmquistite Const Prop Mineral7 18-31

London D (1986) Holmquistite as a guide to pegmatitic rare metaldeposits Econ Geol 81 704-712

Long GJ Cranshaw TE Longworth G (1983) The idealMoumlssbauer effect absorber thickness Moumlssbauer Effect DataJournal 6(2) 42-49

Maresch WV amp Langer K (1976) Synthesis lattice constants andOH-valence vibrations of an orthorhombic amphibole withexcess OH in the system Li2O-MgO-SiO2-H2O ContribMineral Petrol 56 27-34

Monier G amp Robert JL (1986) Muscovite solid solutions in thesystem K2O-MgO-FeO-Al2O3-SiO2-H2O an experimentalstudy at 2 kbar PH2O and comparison with natural Li-free whitemicas Mineral Mag 50 257-266

Oberti R Caballero J-M Ottolini L Andres SL Herreros V(2000) Sodic-ferripedrizite a new monoclinic amphibolebridging the magnesium-iron-manganese-lithium and thesodium-calcium group Am Mineral 85 578-585

326

G Iezzi G Della Ventura G Pedrazzi J-L Robert R Oberti

and little is known about their stability In this paper wedescribe the synthesis and crystal-chemical characteriza-tion of end-member ferri-clinoferroholmquistite

Experimental methods

Starting materials were prepared both as silicate gelsaccording to the method of Hamilton amp Henderson (1968)and as hydroxide-oxides mixtures Iron was introduced inthe gel both as trivalent and as metallic Fe following theprocedure of Monier amp Robert (1986) Hydrothermalsynthesis was done in the T range 500-800degC and in theP(H2O) range 1-7 kbar for a maximum duration of 12 daysThe syntheses were done in two different internally-heatedpressure vessels one for runs below 4 kbar and the otherfor higher P values T was monitored by three mantled-type-K thermocouples (accuracy plusmn 5degC calibrated againstthe melting point of NaCl at 1 atm) and disposed aroundthe hot-spot P was recorded by a transducer (accuracyplusmn 20 bars DallrsquoAgnol et al 1999) In the runs atP pound 4 kbar fO2 conditions were imposed by a H2-Ar gasmixture and fH2 was monitored by a Shaw membrane(Gaillard et al 2001 and references therein) In the runs atP sup3 4 kbar pure Ar was used as the pressure medium thusbuffering the system at NNO+3 (Schmidt et al 1997) The500degC runs were internally buffered due to the low perme-ability to hydrogen of the gold capsule Because the perme-ability to hydrogen of gold is three orders of magnitudelower than that of silver and platinum (Chou 1987) wecompared experiments done under the same P T X condi-tions using both gold or Ag60Pd40 capsules The experimentdone in the gold capsule produced monophase amphibolewhereas that done in Ag60Pd40 gave an assemblage of Li-pyroxene hematite and quartz This evidence confirms thatthe use of gold capsules precludes osmotic equilibrium at500degC for run times of the order of a few weeks

Step-scan X-ray powder patterns were collected at theUniversity of Roma Tre on a Scintag X1 diffractometeroperated in the vertical q-q configuration with Ni-filteredCuKa radiation and a Si(Li) solid-state detector Celldimensions were refined by whole-powder-pattern refine-

ment (Rietveld method) using DBW32 (Wiles amp Young1981)

Room-temperature FTIR spectra in the OH-stretchingregion (4000-3000 cm-1) were collected at the University ofRoma Tre on a Nicolet 760 spectrophotometer equippedwith a DTGS detector and a KBr beamsplitter The nominalresolution is 2 cm-1 spectra are the average of 64 scansSamples were prepared for FTIR spectroscopy as KBrpellets using the procedure of Robert et al (1989a)

For Moumlssbauer data collection samples were powderedin an agate mortar mixed with vaseline gel and placed in aplexiglass sample-holder This method limits preferentialorientation and texture effects The absorber thickness wasestimated on the basis of the mass absorption coefficientsfor 144 keV gamma radiation (Long et al 1983 Rancourtet al 1993) When necessary thickness effects were takeninto account (Lang 1963 Rancourt 1989 Pedrazzi et al1999 and references therein) Spectra were recorded intransmission mode at 297 K with a conventional constant-acceleration Moumlssbauer spectrometer The source was57CoRh with an activity of about 370 MBq (10 mCi)Calibration was done using either a-Fe foil or an SNPabsorber at room temperature Isomer shift are expressedrelative to a-Fe

Results and interpretation of the data

Experimental products

Run powders were studied by optical microscopypowder XRD and SEM Syntheses done at 500degC and pres-sures up to 7 kbar gave an essentially monophase amphi-

322

Fig 1 SEM images of synthetic ferri-clinoferroholmquistite The crystals have an average width of 05 mm and lengths of up 10 mm Noother phases are detectable The scale bar is 2 mm (for both images)

Table 1 Run conditions for synthetic end-member ferri-clinoferro-holmquistite Sample Temperature

bole (plus negligible amounts of quartz) at higher T(sup3 600degC) amphibole is replaced by lithian clinopyroxene(dominant) + magnetite + quartz Amphibole crystals areacicular 05 5 mm on average (Fig 1) Both gels andoxide mixtures gave similar run products but the crystaldimensions obtained from gels are half those obtained fromoxides

X-ray diffraction

The X-ray powder patterns of three samples (101 207and 364 Table 1) were indexed in C2m refined unit-celldimensions are given in Table 2 The unit-cell edges arelonger and the b angle is smaller than the values reportedby Caballero et al (1998) for sodic ferri-clinoferro-holmquistite and by Oberti et al (2003) for ferri-clinofer-roholmquistite with some deviation from idealstoichiometry (namely some Na at M4 Mg at M1 and M3and Li at M3) Differences in the b value can be explainedby the M4Li content and those in the b value by the Mgcontent of the natural samples

Moumlssbauer spectroscopy

The Moumlssbauer spectra of samples 101 207 and 364 arealmost identical the spectrum of sample 101 is shown inFig 2 Refined Moumlssbauer parameters (Table 3) varywithin experimental error for the three samples Threequadrupole doublets were resolved of which two are due toFe2+ (around 22 and 28 mms) and one to Fe3+(03mms)Following Law amp Whittaker (1981) and Hawthorne (1983)the doublet with the largest quadrupole splitting wasassigned to Fe2+ at the M1 site whereas the other wasassigned to Fe2+ at the M3 site (Fig 2) The Fe3+ compo-nent was assigned to the M2 site (Fig 2) The Fe2+ Fe3+

ratio calculated from band areas is close to 32 for all threesamples

FTIR spectroscopy

The infrared spectra in the OH-stretching region fordifferent ferri-clinoferroholmquistite samples obtainedunder different pressure conditions are given in Fig 3They all show one very sharp (full-width-at-half-maximun-height FWHM = 4-5 cm-1) absorption band centred at3614 cm-1 and one minor satellite band at 3644 cm-1 Thepresence of a single band in the OH-spectrum of an amphi-

Synthetic ferri-clinoferroholmquistite 323

Fig 2 The Moumlssbauer spectrum of ferri-clinoferroholmquistite 101

Table 2 Unit-cell parameters for synthetic ferro-clinoferriholmquistite

Table 3 Moumlssbauer parameters for synthetic ferri-clinoferroholmquistite

G Iezzi G Della Ventura G Pedrazzi J-L Robert R Oberti

bole implies the presence of a single cation at the OH-coordinated M1M1M3 octahedra (eg Della Ventura1992) In addition the frequency value (3614 cm-1) iscompatible with the vibration of an O-H bond pointingtoward an empty A-site (Della Ventura 1992 Hawthorne etal 1997) Considering the above arguments and the cationdistribution derived by Moumlssbauer spectroscopy the mainband at 3614 cm-1 is assigned to the Fe2+Fe2+Fe2+-[A] -OHconfiguration From the work of Robert et al (1989b) onsynthetic lepidolites we know that the presence of Li at theoctahedral sites in micas which are closely related toamphiboles induces a +30 cm-1 wavenumber shift of theOH-band The 3644 cm-1 minor absorption is shiftedexactly 30 cm-1 toward higher frequencies with respect tothe main band at 3614 cm-1 therefore it can be assigned tothe Fe2+Fe2+Li-OH-A configuration it shows the pres-ence of a small (but significant) amount of Li at the NNtrimer of octahedra in the first coordination shell aroundthe anion site

The crystal-chemical formula of synthetic ferri-clinoferroholmquistite

The syntheses reported in this work did not providecrystals of a size suitable for X-ray single-crystal refine-ment andor SIMS analysis However the composition ofthe system is constrained to Si Fe Li H and O and theavailable crystal-chemical knowledge combined with FTIRand Moumlssbauer data allowed us to obtain the cation distri-bution Si is the only tetrahedral cation because Fe3+ isconsidered to be exclusively a C-group cation in amphibole(Hawthorne 1983) Moumlssbauer spectra confirm that Fe3+

occurs only in octahedral coordination and allow assign-

ment to the M2 site Moumlssbauer analysis also precludes thepresence of significant Fe2+ at the M4 site and indicatesordering of Fe2+ at the M1 and M3 sites Previous literaturesuggests that Li can be incorporated both at the M4 and atthe M3 sites Low Li contents were also reported at the Asite in a synthetic orthoamphibole (Maresch amp Langer1976) In the samples of this work FTIR analysis showsthat the A-site is empty and that the amount of octahedralLi is very low Thus the chemical formula of ferri-clinofer-roholmquistites synthesized in this work isA B(Li2-x Fe2+

x)C(M1M3Fe2+3-x

M2Fe3+2

M3Lix)TSi8O22(OH)2where the only departure from nominal stoichiometryshown by infrared is an almost negligible amount of Li atM3 (ie x ~ 0) which is locally balanced by Fe3+ at M2(Hawthorne et al 1993) in order to maintain electroneu-trality there must be an equal amount of Fe2+ at M4 whichis too low to be detected by Moumlssbauer spectroscopy Theseconclusions for a simple chemical system are in agreementwith those for the more complex natural samples (Oberti etal 2003)

Ordering of cations in syntheticferri-clinoferroholmquistite

Considerable efforts have been devoted in the lastdecade to characterizing short-range order in amphibolesby infrared spectroscopy (eg Della Ventura et al1996a 1996b 1999 Hawthorne et al 1996a 1996b

324

Fig 3 Infrared spectra in the OH-stretching region ofLi2(Fe2+

3Fe3+2)Si8O22(OH)2 Syntheses were done at 500degC and

variable pressure

Fig 4 The IR OH-stretching spectrum of ferri-clinoferro-holmquistite (a) compared to that of tremolite (b) Cumm =cummingtonite component (Mg at M4)

2000) The FTIR OH-spectrum of ferri-clinoferro-holmquistite (Fig 4a) albeit extremely simple can beused to derive useful information based on band multi-plicity and band widths

It is well known that the presence of two cations at theoctahedral sites directly bonded to the hydroxyl groupgives rise to four bands in the infrared OH-stretchingregion which can be assigned to the four possible config-urations (Strens 1966 Hawthorne et al 1996b DellaVentura 1992) The presence of a single band in the spec-trum of ferri-clinoferroholmquistite indicates that there isa single cation at the M1 and M3 sites which in turnimplies ordering of Fe3+ at the M2 site which is not coor-dinated to OH This result is in accord with the X-raysingle-crystal work of Caballero et al (1998) and Obertiet al (2000 2003) which shows that Fe3+ is stronglyordered at the M2 site in all Li-rich amphiboles so farrefined The small band at 3644 cm-1 also conf irms thatoctahedral Li is ordered at either the M1 or the M3 sitesin agreement with all structure refinements done onnatural samples from Pedriza (Caballero et al 1998Oberti et al 2000 2003) or on Li-bearing sodic amphi-boles (Hawthorne et al 1993 1994) which indicate thatCLi is ordered at M3

The presence of different cations at the sites involvedin the absorption is known to give rise to signif icant bandbroadening (ldquosubstitutional broadeningrdquo Strens 1974)Again the spectrum of ferri-clinoferroholmquistite hasvery sharp bands this situation has been found so faronly in tremolite (Fig 4) which is a strongly orderedamphibole (Hawthorne 1997) with an empty A site M4occupied by Ca (plus minor Mg Hawthorne et al 2000and references therein) and the three octahedral sitesoccupied by Mg The local cummingtonite environmentin tremolite gives rise to a well-defined component in thespectrum at 3668 cm-1 (arrowed in Fig 4) Cationdisorder at sites not directly bonded to OH such as thepresence of a cation at the A-site or the Na-Ca disorder atthe NNN M4 site strongly affects the OH-stretchingband width (Hawthorne et al 1997) The very sharpFWHM of the single main band in the spectrum of ferri-clinoferroholmquistite is therefore indicative ofextremely low amounts of Fe2+ at M4 and consequentlyof Li at M3

The local configuration around the OH-group in ferri-clinoferroholmquistite is identical to that in ferroactinoliteie FeFeFe-OH-A -SiSi (notation introduced by DellaVentura et al 1999) On the other hand the wavenumberof this band in ferri-clinoferroholmquistite is 10 cm-1 lowerthan in ferro-actinolite (Fig 5) Changes in cation occu-pancy at the NNN M2 site may also give rise to band split-ting and shift (Della Ventura et al 1999) For example inpargasites and Al-bearing tremolites there is a downwardshift of ~ 20 cm-1 due to the presence of Al at the M2 site(Hawthorne et al 2000) We tentatively attribute the down-ward shift of 10 cm-1 observed in ferri-clinoferroholmquis-tite relative to ferro-actinolite to the NNN effect of Fe3+ atthe M2 site However this point needs further experimentalsupport as cation disorder at M4 can also induce a similarshift

Conclusions

Ferri-clinoferroholmquistite Li2(Fe2+3Fe3+

2)Si8O22(OH)2 has been obtained in a very limited temperaturerange between 500-600degC for a wide pressure range(1-7 kbar) For T sup3 600degC it is replaced by an assemblageof pyroxene + magnetite + quartz These results confirmthe prediction based on petrological observation of Obertiet al (2003) on the upper thermal stability of this type ofLi-rich amphiboles Spectroscopic data show that ferri-clinoferroholmquistite has a strongly ordered cationarrangement in agreement with the prediction ofHawthorne (1997) on local bond-valence ground and withsingle-crystal refinements on Li-rich amphiboles (egCaballero et al 1998 Oberti et al 2000 2003)Moumlssbauer and infrared spectroscopy can be extremelyuseful in characterizing both long-range and short-rangeorder in synthetic phases which cannot be adequately char-acterised by EMP analysis and X-ray structure refinement

Acknowledgements We thank Bruno Di Sabatino forconstructive comments at the beginning of the workAnnibale Mottana and Ciriaco Giampaolo allowed us useof the analytical facilities at the University of Roma TreThanks are due to Sergio Lomastro for assistance in X-ray data collection and to Arnaud Papin Jacques Rouxand Bruno Scaillet for technical assistance duringsynthesis Part of this work was done during the stay of

Synthetic ferri-clinoferroholmquistite 325

Fig 5 The IR OH-stretching spectrum of ferri-clinoferro-holmquistite compared to that of ferro-actinolite (sample MH13Della Ventura unpublished)

G Iezzi G Della Ventura G Pedrazzi J-L Robert R Oberti

GI at ISTO-CNRS (Orleacuteans) financed by theUniversity of Chieti and an EGIDE-Italian ForeignAffairs Ministry fellowships The constructive criticismof referees Walter Maresch and Frank C Hawthorne isalso acknowledged

References

Boffa Ballaran T Angel RJ Carpenter MA (2000) High pres-sure transformation behaviour of the cummingtonite-gruneritesolid-solution Eur J Mineral 12 1195-1213

Boffa Ballaran T Carpenter MA Domeneghetti MC (2001)Phase transition and thermodynamic mixing behaviour of thecummingtonite-grunerite solid-solution Phys ChemMinerals 28 87-101

Caballero J-M Monge A La Iglesia A Tornos F (1998) Ferri-clinoholmquistite Li2(Fe2+Mg)Fe3+

2Si8O22(OH)2 a new BLiclinoamphibole from the Pedriza Massif Sierra deGuadarrama Spanish Central System Am Mineral 83 167-171

Chou IM (1987) Oxygen buffer and hydrogen sensor techniqueat elevated pressures and temperatures In ldquoHydrothermalexperiments techniquesrdquo (HL Barnes amp GC Ulmer eds)Wiley New York

DallrsquoAgnol R Scaillet B Pichavant M (1999) An experimentalstudy of a lower Proterozoic A-type granite from the EasternAmazonian Craton Brazil J Petrol 40 1673-1698

Deer WA Howie RA Zussman J (1999) Rock formingminerals Double-chain Silicates Ed Longman Scientific ampTechnical pp 692

Della Ventura G (1992) Recent developments in the synthesis andcharacterization of amphiboles Synthesis and crystal-chem-istry of richterites Trends in Mineralogy 1 153-192

Della Ventura G Robert JL Hawthorne FC (1996a) Infraredspectroscopy of synthetic (NiMgCo)-potassium-richterite InldquoMineral Spectroscopy a tribute to Roger G Burnsrdquo (MDDyar C McCammon and MW Schaefer eds) The Geoche-mical Society Special Publication 5 55-63

Della Ventura G Robert J-L Hawthorne FC Prost R (1996b)Short-range disorder of Si and Ti in the tetrahedral double-chain unit of synthetic Ti-bearing potassium-richterite AmMineral 81 56-60

Della Ventura G Hawthorne FC Robert J-L Delbove FWelch MD Raudsepp M (1999) Short-range order ofcations in synthetic amphiboles along the richterite - pargasitejoin Eur J Mineral 11 79-94

Gaillard F Scaillet B Pichavant M Beacuteny JM (2001) Theeffect of water and fO2 on the ferric-ferrous ratio of silicicmelts Chem Geol 174 255-273

Ginzburg IV (1965) Holmquistite and its structural variant-clino-holmquistite Trudy Min Muz Akad Nauk USSR 16 73-89 (inRussian)

Hamilton DL amp Henderson CMB (1968) The preparation ofsilicate compositions by a gelling method Mineral Mag 36832ndash838

Hawthorne FC (1983) The crystal chemistry of the amphibolesCan Mineral 21 174-481

mdash (1997) Short-range order in amphiboles a bond-valenceapproach Can Mineral 35 201-216

Hawthorne FC Ungaretti L Oberti R Bottazzi P (1993) LiAn important component in igneous alkali amphiboles AmMineral 78 733-745

Hawthorne FC Ungaretti L Oberti R Cannillo E (1994) Themechanism of Li incorporation in amphiboles Am Mineral79 443-451

Hawthorne FC Della Ventura G Robert J-L (1996a) Short-range order of (NaK) and Al in tremolite An infrared studyAm Mineral 81 782-784

Hawthorne FC Della Ventura G Robert J-L (1996b) Short-range order and long-range order in amphiboles A model forthe interpretation of infrared spectra in the principal OH-stretching region In ldquoMineral Spectroscopy a tribute to RogerG Burnsrdquo (MD Dyar C McCammon and MW Schaefereds) The Geochemical Society Special Publication 5 49-54

Hawthorne FC Della Ventura G Robert J-L Welch MDRaudsepp M Jenkins DM (1997) A Rietveld and infraredstudy of synthetic amphiboles along the potassium-richterite -tremolite join Am Mineral 82 708-716

Hawthorne FC Welch MD Della Ventura G Shuangxi LiuRobert J-L Jenkins DM (2000) Short-range order insynthetic aluminous tremolites an infrared and triple-quantumMAS NMR study Am Mineral 85 1716-1724

Hirschmann M Evans BW Yang H (1994) Composition andtemperature dependence of Fe-Mg ordering in cummingtonite-grunerite as determined by X-ray diffraction Am Mineral 79862-877

Irusteta MC amp Whittaker EJW (1975) A three dimensionalrefinement of the structure of holmquistite Acta Cryst B31145-150

Lang G (1963) Interpretation of experimental Moumlssbauer spec-trum areas Nucl Inst and Meth 24 425- 428

Law AD amp Whittaker EJ (1981) Studies of the orthoamphiboles1 ndash The Moumlssbauer and infrared spectra of holmquistite BullMineacuteral 104 381-386

Leake BE Woolley AR Arps CES BirchWD Gilbert MCGrice JD Hawthorne FC Kato A Kisch HJ KrivovichevVG Linthout K Laird J Mandarino JA Maresch WVNickel EH Rock NMS Schumacher JC Smith DCUngaretti L Whittacker EJW Youzhi G (1997)Nomenclature of amphiboles Report of the subcommitte onamphiboles of the International Mineralogical Associationcommission on new minerals and minerals name Eur JMineral 9 623-651

Litvin AL amp Petrunina AA (1975) On the crystal structure ofclinoholmquistite Konst Svoistva Mineral 8 6-8 (in Russian)

Litvin AL Ginzburg IV Egorova LN Ostapenko SS (1973)On the crystal structure of holmquistite Const Prop Mineral7 18-31

London D (1986) Holmquistite as a guide to pegmatitic rare metaldeposits Econ Geol 81 704-712

Long GJ Cranshaw TE Longworth G (1983) The idealMoumlssbauer effect absorber thickness Moumlssbauer Effect DataJournal 6(2) 42-49

Maresch WV amp Langer K (1976) Synthesis lattice constants andOH-valence vibrations of an orthorhombic amphibole withexcess OH in the system Li2O-MgO-SiO2-H2O ContribMineral Petrol 56 27-34

Monier G amp Robert JL (1986) Muscovite solid solutions in thesystem K2O-MgO-FeO-Al2O3-SiO2-H2O an experimentalstudy at 2 kbar PH2O and comparison with natural Li-free whitemicas Mineral Mag 50 257-266

Oberti R Caballero J-M Ottolini L Andres SL Herreros V(2000) Sodic-ferripedrizite a new monoclinic amphibolebridging the magnesium-iron-manganese-lithium and thesodium-calcium group Am Mineral 85 578-585

326

bole (plus negligible amounts of quartz) at higher T(sup3 600degC) amphibole is replaced by lithian clinopyroxene(dominant) + magnetite + quartz Amphibole crystals areacicular 05 5 mm on average (Fig 1) Both gels andoxide mixtures gave similar run products but the crystaldimensions obtained from gels are half those obtained fromoxides

X-ray diffraction

The X-ray powder patterns of three samples (101 207and 364 Table 1) were indexed in C2m refined unit-celldimensions are given in Table 2 The unit-cell edges arelonger and the b angle is smaller than the values reportedby Caballero et al (1998) for sodic ferri-clinoferro-holmquistite and by Oberti et al (2003) for ferri-clinofer-roholmquistite with some deviation from idealstoichiometry (namely some Na at M4 Mg at M1 and M3and Li at M3) Differences in the b value can be explainedby the M4Li content and those in the b value by the Mgcontent of the natural samples

Moumlssbauer spectroscopy

The Moumlssbauer spectra of samples 101 207 and 364 arealmost identical the spectrum of sample 101 is shown inFig 2 Refined Moumlssbauer parameters (Table 3) varywithin experimental error for the three samples Threequadrupole doublets were resolved of which two are due toFe2+ (around 22 and 28 mms) and one to Fe3+(03mms)Following Law amp Whittaker (1981) and Hawthorne (1983)the doublet with the largest quadrupole splitting wasassigned to Fe2+ at the M1 site whereas the other wasassigned to Fe2+ at the M3 site (Fig 2) The Fe3+ compo-nent was assigned to the M2 site (Fig 2) The Fe2+ Fe3+

ratio calculated from band areas is close to 32 for all threesamples

FTIR spectroscopy

The infrared spectra in the OH-stretching region fordifferent ferri-clinoferroholmquistite samples obtainedunder different pressure conditions are given in Fig 3They all show one very sharp (full-width-at-half-maximun-height FWHM = 4-5 cm-1) absorption band centred at3614 cm-1 and one minor satellite band at 3644 cm-1 Thepresence of a single band in the OH-spectrum of an amphi-

Synthetic ferri-clinoferroholmquistite 323

Fig 2 The Moumlssbauer spectrum of ferri-clinoferroholmquistite 101

Table 2 Unit-cell parameters for synthetic ferro-clinoferriholmquistite

Table 3 Moumlssbauer parameters for synthetic ferri-clinoferroholmquistite

G Iezzi G Della Ventura G Pedrazzi J-L Robert R Oberti

bole implies the presence of a single cation at the OH-coordinated M1M1M3 octahedra (eg Della Ventura1992) In addition the frequency value (3614 cm-1) iscompatible with the vibration of an O-H bond pointingtoward an empty A-site (Della Ventura 1992 Hawthorne etal 1997) Considering the above arguments and the cationdistribution derived by Moumlssbauer spectroscopy the mainband at 3614 cm-1 is assigned to the Fe2+Fe2+Fe2+-[A] -OHconfiguration From the work of Robert et al (1989b) onsynthetic lepidolites we know that the presence of Li at theoctahedral sites in micas which are closely related toamphiboles induces a +30 cm-1 wavenumber shift of theOH-band The 3644 cm-1 minor absorption is shiftedexactly 30 cm-1 toward higher frequencies with respect tothe main band at 3614 cm-1 therefore it can be assigned tothe Fe2+Fe2+Li-OH-A configuration it shows the pres-ence of a small (but significant) amount of Li at the NNtrimer of octahedra in the first coordination shell aroundthe anion site

The crystal-chemical formula of synthetic ferri-clinoferroholmquistite

The syntheses reported in this work did not providecrystals of a size suitable for X-ray single-crystal refine-ment andor SIMS analysis However the composition ofthe system is constrained to Si Fe Li H and O and theavailable crystal-chemical knowledge combined with FTIRand Moumlssbauer data allowed us to obtain the cation distri-bution Si is the only tetrahedral cation because Fe3+ isconsidered to be exclusively a C-group cation in amphibole(Hawthorne 1983) Moumlssbauer spectra confirm that Fe3+

occurs only in octahedral coordination and allow assign-

ment to the M2 site Moumlssbauer analysis also precludes thepresence of significant Fe2+ at the M4 site and indicatesordering of Fe2+ at the M1 and M3 sites Previous literaturesuggests that Li can be incorporated both at the M4 and atthe M3 sites Low Li contents were also reported at the Asite in a synthetic orthoamphibole (Maresch amp Langer1976) In the samples of this work FTIR analysis showsthat the A-site is empty and that the amount of octahedralLi is very low Thus the chemical formula of ferri-clinofer-roholmquistites synthesized in this work isA B(Li2-x Fe2+

x)C(M1M3Fe2+3-x

M2Fe3+2

M3Lix)TSi8O22(OH)2where the only departure from nominal stoichiometryshown by infrared is an almost negligible amount of Li atM3 (ie x ~ 0) which is locally balanced by Fe3+ at M2(Hawthorne et al 1993) in order to maintain electroneu-trality there must be an equal amount of Fe2+ at M4 whichis too low to be detected by Moumlssbauer spectroscopy Theseconclusions for a simple chemical system are in agreementwith those for the more complex natural samples (Oberti etal 2003)

Ordering of cations in syntheticferri-clinoferroholmquistite

Considerable efforts have been devoted in the lastdecade to characterizing short-range order in amphibolesby infrared spectroscopy (eg Della Ventura et al1996a 1996b 1999 Hawthorne et al 1996a 1996b

324

Fig 3 Infrared spectra in the OH-stretching region ofLi2(Fe2+

3Fe3+2)Si8O22(OH)2 Syntheses were done at 500degC and

variable pressure

Fig 4 The IR OH-stretching spectrum of ferri-clinoferro-holmquistite (a) compared to that of tremolite (b) Cumm =cummingtonite component (Mg at M4)

2000) The FTIR OH-spectrum of ferri-clinoferro-holmquistite (Fig 4a) albeit extremely simple can beused to derive useful information based on band multi-plicity and band widths

It is well known that the presence of two cations at theoctahedral sites directly bonded to the hydroxyl groupgives rise to four bands in the infrared OH-stretchingregion which can be assigned to the four possible config-urations (Strens 1966 Hawthorne et al 1996b DellaVentura 1992) The presence of a single band in the spec-trum of ferri-clinoferroholmquistite indicates that there isa single cation at the M1 and M3 sites which in turnimplies ordering of Fe3+ at the M2 site which is not coor-dinated to OH This result is in accord with the X-raysingle-crystal work of Caballero et al (1998) and Obertiet al (2000 2003) which shows that Fe3+ is stronglyordered at the M2 site in all Li-rich amphiboles so farrefined The small band at 3644 cm-1 also conf irms thatoctahedral Li is ordered at either the M1 or the M3 sitesin agreement with all structure refinements done onnatural samples from Pedriza (Caballero et al 1998Oberti et al 2000 2003) or on Li-bearing sodic amphi-boles (Hawthorne et al 1993 1994) which indicate thatCLi is ordered at M3

The presence of different cations at the sites involvedin the absorption is known to give rise to signif icant bandbroadening (ldquosubstitutional broadeningrdquo Strens 1974)Again the spectrum of ferri-clinoferroholmquistite hasvery sharp bands this situation has been found so faronly in tremolite (Fig 4) which is a strongly orderedamphibole (Hawthorne 1997) with an empty A site M4occupied by Ca (plus minor Mg Hawthorne et al 2000and references therein) and the three octahedral sitesoccupied by Mg The local cummingtonite environmentin tremolite gives rise to a well-defined component in thespectrum at 3668 cm-1 (arrowed in Fig 4) Cationdisorder at sites not directly bonded to OH such as thepresence of a cation at the A-site or the Na-Ca disorder atthe NNN M4 site strongly affects the OH-stretchingband width (Hawthorne et al 1997) The very sharpFWHM of the single main band in the spectrum of ferri-clinoferroholmquistite is therefore indicative ofextremely low amounts of Fe2+ at M4 and consequentlyof Li at M3

The local configuration around the OH-group in ferri-clinoferroholmquistite is identical to that in ferroactinoliteie FeFeFe-OH-A -SiSi (notation introduced by DellaVentura et al 1999) On the other hand the wavenumberof this band in ferri-clinoferroholmquistite is 10 cm-1 lowerthan in ferro-actinolite (Fig 5) Changes in cation occu-pancy at the NNN M2 site may also give rise to band split-ting and shift (Della Ventura et al 1999) For example inpargasites and Al-bearing tremolites there is a downwardshift of ~ 20 cm-1 due to the presence of Al at the M2 site(Hawthorne et al 2000) We tentatively attribute the down-ward shift of 10 cm-1 observed in ferri-clinoferroholmquis-tite relative to ferro-actinolite to the NNN effect of Fe3+ atthe M2 site However this point needs further experimentalsupport as cation disorder at M4 can also induce a similarshift

Conclusions

Ferri-clinoferroholmquistite Li2(Fe2+3Fe3+

2)Si8O22(OH)2 has been obtained in a very limited temperaturerange between 500-600degC for a wide pressure range(1-7 kbar) For T sup3 600degC it is replaced by an assemblageof pyroxene + magnetite + quartz These results confirmthe prediction based on petrological observation of Obertiet al (2003) on the upper thermal stability of this type ofLi-rich amphiboles Spectroscopic data show that ferri-clinoferroholmquistite has a strongly ordered cationarrangement in agreement with the prediction ofHawthorne (1997) on local bond-valence ground and withsingle-crystal refinements on Li-rich amphiboles (egCaballero et al 1998 Oberti et al 2000 2003)Moumlssbauer and infrared spectroscopy can be extremelyuseful in characterizing both long-range and short-rangeorder in synthetic phases which cannot be adequately char-acterised by EMP analysis and X-ray structure refinement

Acknowledgements We thank Bruno Di Sabatino forconstructive comments at the beginning of the workAnnibale Mottana and Ciriaco Giampaolo allowed us useof the analytical facilities at the University of Roma TreThanks are due to Sergio Lomastro for assistance in X-ray data collection and to Arnaud Papin Jacques Rouxand Bruno Scaillet for technical assistance duringsynthesis Part of this work was done during the stay of

Synthetic ferri-clinoferroholmquistite 325

Fig 5 The IR OH-stretching spectrum of ferri-clinoferro-holmquistite compared to that of ferro-actinolite (sample MH13Della Ventura unpublished)

G Iezzi G Della Ventura G Pedrazzi J-L Robert R Oberti

GI at ISTO-CNRS (Orleacuteans) financed by theUniversity of Chieti and an EGIDE-Italian ForeignAffairs Ministry fellowships The constructive criticismof referees Walter Maresch and Frank C Hawthorne isalso acknowledged

References

Boffa Ballaran T Angel RJ Carpenter MA (2000) High pres-sure transformation behaviour of the cummingtonite-gruneritesolid-solution Eur J Mineral 12 1195-1213

Boffa Ballaran T Carpenter MA Domeneghetti MC (2001)Phase transition and thermodynamic mixing behaviour of thecummingtonite-grunerite solid-solution Phys ChemMinerals 28 87-101

Caballero J-M Monge A La Iglesia A Tornos F (1998) Ferri-clinoholmquistite Li2(Fe2+Mg)Fe3+

2Si8O22(OH)2 a new BLiclinoamphibole from the Pedriza Massif Sierra deGuadarrama Spanish Central System Am Mineral 83 167-171

Chou IM (1987) Oxygen buffer and hydrogen sensor techniqueat elevated pressures and temperatures In ldquoHydrothermalexperiments techniquesrdquo (HL Barnes amp GC Ulmer eds)Wiley New York

DallrsquoAgnol R Scaillet B Pichavant M (1999) An experimentalstudy of a lower Proterozoic A-type granite from the EasternAmazonian Craton Brazil J Petrol 40 1673-1698

Deer WA Howie RA Zussman J (1999) Rock formingminerals Double-chain Silicates Ed Longman Scientific ampTechnical pp 692

Della Ventura G (1992) Recent developments in the synthesis andcharacterization of amphiboles Synthesis and crystal-chem-istry of richterites Trends in Mineralogy 1 153-192

Della Ventura G Robert JL Hawthorne FC (1996a) Infraredspectroscopy of synthetic (NiMgCo)-potassium-richterite InldquoMineral Spectroscopy a tribute to Roger G Burnsrdquo (MDDyar C McCammon and MW Schaefer eds) The Geoche-mical Society Special Publication 5 55-63

Della Ventura G Robert J-L Hawthorne FC Prost R (1996b)Short-range disorder of Si and Ti in the tetrahedral double-chain unit of synthetic Ti-bearing potassium-richterite AmMineral 81 56-60

Della Ventura G Hawthorne FC Robert J-L Delbove FWelch MD Raudsepp M (1999) Short-range order ofcations in synthetic amphiboles along the richterite - pargasitejoin Eur J Mineral 11 79-94

Gaillard F Scaillet B Pichavant M Beacuteny JM (2001) Theeffect of water and fO2 on the ferric-ferrous ratio of silicicmelts Chem Geol 174 255-273

Ginzburg IV (1965) Holmquistite and its structural variant-clino-holmquistite Trudy Min Muz Akad Nauk USSR 16 73-89 (inRussian)

Hamilton DL amp Henderson CMB (1968) The preparation ofsilicate compositions by a gelling method Mineral Mag 36832ndash838

Hawthorne FC (1983) The crystal chemistry of the amphibolesCan Mineral 21 174-481

mdash (1997) Short-range order in amphiboles a bond-valenceapproach Can Mineral 35 201-216

Hawthorne FC Ungaretti L Oberti R Bottazzi P (1993) LiAn important component in igneous alkali amphiboles AmMineral 78 733-745

Hawthorne FC Ungaretti L Oberti R Cannillo E (1994) Themechanism of Li incorporation in amphiboles Am Mineral79 443-451

Hawthorne FC Della Ventura G Robert J-L (1996a) Short-range order of (NaK) and Al in tremolite An infrared studyAm Mineral 81 782-784

Hawthorne FC Della Ventura G Robert J-L (1996b) Short-range order and long-range order in amphiboles A model forthe interpretation of infrared spectra in the principal OH-stretching region In ldquoMineral Spectroscopy a tribute to RogerG Burnsrdquo (MD Dyar C McCammon and MW Schaefereds) The Geochemical Society Special Publication 5 49-54

Hawthorne FC Della Ventura G Robert J-L Welch MDRaudsepp M Jenkins DM (1997) A Rietveld and infraredstudy of synthetic amphiboles along the potassium-richterite -tremolite join Am Mineral 82 708-716

Hawthorne FC Welch MD Della Ventura G Shuangxi LiuRobert J-L Jenkins DM (2000) Short-range order insynthetic aluminous tremolites an infrared and triple-quantumMAS NMR study Am Mineral 85 1716-1724

Hirschmann M Evans BW Yang H (1994) Composition andtemperature dependence of Fe-Mg ordering in cummingtonite-grunerite as determined by X-ray diffraction Am Mineral 79862-877

Irusteta MC amp Whittaker EJW (1975) A three dimensionalrefinement of the structure of holmquistite Acta Cryst B31145-150

Lang G (1963) Interpretation of experimental Moumlssbauer spec-trum areas Nucl Inst and Meth 24 425- 428

Law AD amp Whittaker EJ (1981) Studies of the orthoamphiboles1 ndash The Moumlssbauer and infrared spectra of holmquistite BullMineacuteral 104 381-386

Leake BE Woolley AR Arps CES BirchWD Gilbert MCGrice JD Hawthorne FC Kato A Kisch HJ KrivovichevVG Linthout K Laird J Mandarino JA Maresch WVNickel EH Rock NMS Schumacher JC Smith DCUngaretti L Whittacker EJW Youzhi G (1997)Nomenclature of amphiboles Report of the subcommitte onamphiboles of the International Mineralogical Associationcommission on new minerals and minerals name Eur JMineral 9 623-651

Litvin AL amp Petrunina AA (1975) On the crystal structure ofclinoholmquistite Konst Svoistva Mineral 8 6-8 (in Russian)

Litvin AL Ginzburg IV Egorova LN Ostapenko SS (1973)On the crystal structure of holmquistite Const Prop Mineral7 18-31

London D (1986) Holmquistite as a guide to pegmatitic rare metaldeposits Econ Geol 81 704-712

Long GJ Cranshaw TE Longworth G (1983) The idealMoumlssbauer effect absorber thickness Moumlssbauer Effect DataJournal 6(2) 42-49

Maresch WV amp Langer K (1976) Synthesis lattice constants andOH-valence vibrations of an orthorhombic amphibole withexcess OH in the system Li2O-MgO-SiO2-H2O ContribMineral Petrol 56 27-34

Monier G amp Robert JL (1986) Muscovite solid solutions in thesystem K2O-MgO-FeO-Al2O3-SiO2-H2O an experimentalstudy at 2 kbar PH2O and comparison with natural Li-free whitemicas Mineral Mag 50 257-266

Oberti R Caballero J-M Ottolini L Andres SL Herreros V(2000) Sodic-ferripedrizite a new monoclinic amphibolebridging the magnesium-iron-manganese-lithium and thesodium-calcium group Am Mineral 85 578-585

326

G Iezzi G Della Ventura G Pedrazzi J-L Robert R Oberti

bole implies the presence of a single cation at the OH-coordinated M1M1M3 octahedra (eg Della Ventura1992) In addition the frequency value (3614 cm-1) iscompatible with the vibration of an O-H bond pointingtoward an empty A-site (Della Ventura 1992 Hawthorne etal 1997) Considering the above arguments and the cationdistribution derived by Moumlssbauer spectroscopy the mainband at 3614 cm-1 is assigned to the Fe2+Fe2+Fe2+-[A] -OHconfiguration From the work of Robert et al (1989b) onsynthetic lepidolites we know that the presence of Li at theoctahedral sites in micas which are closely related toamphiboles induces a +30 cm-1 wavenumber shift of theOH-band The 3644 cm-1 minor absorption is shiftedexactly 30 cm-1 toward higher frequencies with respect tothe main band at 3614 cm-1 therefore it can be assigned tothe Fe2+Fe2+Li-OH-A configuration it shows the pres-ence of a small (but significant) amount of Li at the NNtrimer of octahedra in the first coordination shell aroundthe anion site

The crystal-chemical formula of synthetic ferri-clinoferroholmquistite

The syntheses reported in this work did not providecrystals of a size suitable for X-ray single-crystal refine-ment andor SIMS analysis However the composition ofthe system is constrained to Si Fe Li H and O and theavailable crystal-chemical knowledge combined with FTIRand Moumlssbauer data allowed us to obtain the cation distri-bution Si is the only tetrahedral cation because Fe3+ isconsidered to be exclusively a C-group cation in amphibole(Hawthorne 1983) Moumlssbauer spectra confirm that Fe3+

occurs only in octahedral coordination and allow assign-

ment to the M2 site Moumlssbauer analysis also precludes thepresence of significant Fe2+ at the M4 site and indicatesordering of Fe2+ at the M1 and M3 sites Previous literaturesuggests that Li can be incorporated both at the M4 and atthe M3 sites Low Li contents were also reported at the Asite in a synthetic orthoamphibole (Maresch amp Langer1976) In the samples of this work FTIR analysis showsthat the A-site is empty and that the amount of octahedralLi is very low Thus the chemical formula of ferri-clinofer-roholmquistites synthesized in this work isA B(Li2-x Fe2+

x)C(M1M3Fe2+3-x

M2Fe3+2

M3Lix)TSi8O22(OH)2where the only departure from nominal stoichiometryshown by infrared is an almost negligible amount of Li atM3 (ie x ~ 0) which is locally balanced by Fe3+ at M2(Hawthorne et al 1993) in order to maintain electroneu-trality there must be an equal amount of Fe2+ at M4 whichis too low to be detected by Moumlssbauer spectroscopy Theseconclusions for a simple chemical system are in agreementwith those for the more complex natural samples (Oberti etal 2003)

Ordering of cations in syntheticferri-clinoferroholmquistite

Considerable efforts have been devoted in the lastdecade to characterizing short-range order in amphibolesby infrared spectroscopy (eg Della Ventura et al1996a 1996b 1999 Hawthorne et al 1996a 1996b

324

Fig 3 Infrared spectra in the OH-stretching region ofLi2(Fe2+

3Fe3+2)Si8O22(OH)2 Syntheses were done at 500degC and

variable pressure

Fig 4 The IR OH-stretching spectrum of ferri-clinoferro-holmquistite (a) compared to that of tremolite (b) Cumm =cummingtonite component (Mg at M4)

2000) The FTIR OH-spectrum of ferri-clinoferro-holmquistite (Fig 4a) albeit extremely simple can beused to derive useful information based on band multi-plicity and band widths

It is well known that the presence of two cations at theoctahedral sites directly bonded to the hydroxyl groupgives rise to four bands in the infrared OH-stretchingregion which can be assigned to the four possible config-urations (Strens 1966 Hawthorne et al 1996b DellaVentura 1992) The presence of a single band in the spec-trum of ferri-clinoferroholmquistite indicates that there isa single cation at the M1 and M3 sites which in turnimplies ordering of Fe3+ at the M2 site which is not coor-dinated to OH This result is in accord with the X-raysingle-crystal work of Caballero et al (1998) and Obertiet al (2000 2003) which shows that Fe3+ is stronglyordered at the M2 site in all Li-rich amphiboles so farrefined The small band at 3644 cm-1 also conf irms thatoctahedral Li is ordered at either the M1 or the M3 sitesin agreement with all structure refinements done onnatural samples from Pedriza (Caballero et al 1998Oberti et al 2000 2003) or on Li-bearing sodic amphi-boles (Hawthorne et al 1993 1994) which indicate thatCLi is ordered at M3

The presence of different cations at the sites involvedin the absorption is known to give rise to signif icant bandbroadening (ldquosubstitutional broadeningrdquo Strens 1974)Again the spectrum of ferri-clinoferroholmquistite hasvery sharp bands this situation has been found so faronly in tremolite (Fig 4) which is a strongly orderedamphibole (Hawthorne 1997) with an empty A site M4occupied by Ca (plus minor Mg Hawthorne et al 2000and references therein) and the three octahedral sitesoccupied by Mg The local cummingtonite environmentin tremolite gives rise to a well-defined component in thespectrum at 3668 cm-1 (arrowed in Fig 4) Cationdisorder at sites not directly bonded to OH such as thepresence of a cation at the A-site or the Na-Ca disorder atthe NNN M4 site strongly affects the OH-stretchingband width (Hawthorne et al 1997) The very sharpFWHM of the single main band in the spectrum of ferri-clinoferroholmquistite is therefore indicative ofextremely low amounts of Fe2+ at M4 and consequentlyof Li at M3

The local configuration around the OH-group in ferri-clinoferroholmquistite is identical to that in ferroactinoliteie FeFeFe-OH-A -SiSi (notation introduced by DellaVentura et al 1999) On the other hand the wavenumberof this band in ferri-clinoferroholmquistite is 10 cm-1 lowerthan in ferro-actinolite (Fig 5) Changes in cation occu-pancy at the NNN M2 site may also give rise to band split-ting and shift (Della Ventura et al 1999) For example inpargasites and Al-bearing tremolites there is a downwardshift of ~ 20 cm-1 due to the presence of Al at the M2 site(Hawthorne et al 2000) We tentatively attribute the down-ward shift of 10 cm-1 observed in ferri-clinoferroholmquis-tite relative to ferro-actinolite to the NNN effect of Fe3+ atthe M2 site However this point needs further experimentalsupport as cation disorder at M4 can also induce a similarshift

Conclusions

Ferri-clinoferroholmquistite Li2(Fe2+3Fe3+

2)Si8O22(OH)2 has been obtained in a very limited temperaturerange between 500-600degC for a wide pressure range(1-7 kbar) For T sup3 600degC it is replaced by an assemblageof pyroxene + magnetite + quartz These results confirmthe prediction based on petrological observation of Obertiet al (2003) on the upper thermal stability of this type ofLi-rich amphiboles Spectroscopic data show that ferri-clinoferroholmquistite has a strongly ordered cationarrangement in agreement with the prediction ofHawthorne (1997) on local bond-valence ground and withsingle-crystal refinements on Li-rich amphiboles (egCaballero et al 1998 Oberti et al 2000 2003)Moumlssbauer and infrared spectroscopy can be extremelyuseful in characterizing both long-range and short-rangeorder in synthetic phases which cannot be adequately char-acterised by EMP analysis and X-ray structure refinement

Acknowledgements We thank Bruno Di Sabatino forconstructive comments at the beginning of the workAnnibale Mottana and Ciriaco Giampaolo allowed us useof the analytical facilities at the University of Roma TreThanks are due to Sergio Lomastro for assistance in X-ray data collection and to Arnaud Papin Jacques Rouxand Bruno Scaillet for technical assistance duringsynthesis Part of this work was done during the stay of

Synthetic ferri-clinoferroholmquistite 325

Fig 5 The IR OH-stretching spectrum of ferri-clinoferro-holmquistite compared to that of ferro-actinolite (sample MH13Della Ventura unpublished)

G Iezzi G Della Ventura G Pedrazzi J-L Robert R Oberti

GI at ISTO-CNRS (Orleacuteans) financed by theUniversity of Chieti and an EGIDE-Italian ForeignAffairs Ministry fellowships The constructive criticismof referees Walter Maresch and Frank C Hawthorne isalso acknowledged

References

Boffa Ballaran T Angel RJ Carpenter MA (2000) High pres-sure transformation behaviour of the cummingtonite-gruneritesolid-solution Eur J Mineral 12 1195-1213

Boffa Ballaran T Carpenter MA Domeneghetti MC (2001)Phase transition and thermodynamic mixing behaviour of thecummingtonite-grunerite solid-solution Phys ChemMinerals 28 87-101

Caballero J-M Monge A La Iglesia A Tornos F (1998) Ferri-clinoholmquistite Li2(Fe2+Mg)Fe3+

2Si8O22(OH)2 a new BLiclinoamphibole from the Pedriza Massif Sierra deGuadarrama Spanish Central System Am Mineral 83 167-171

Chou IM (1987) Oxygen buffer and hydrogen sensor techniqueat elevated pressures and temperatures In ldquoHydrothermalexperiments techniquesrdquo (HL Barnes amp GC Ulmer eds)Wiley New York

DallrsquoAgnol R Scaillet B Pichavant M (1999) An experimentalstudy of a lower Proterozoic A-type granite from the EasternAmazonian Craton Brazil J Petrol 40 1673-1698

Deer WA Howie RA Zussman J (1999) Rock formingminerals Double-chain Silicates Ed Longman Scientific ampTechnical pp 692

Della Ventura G (1992) Recent developments in the synthesis andcharacterization of amphiboles Synthesis and crystal-chem-istry of richterites Trends in Mineralogy 1 153-192

Della Ventura G Robert JL Hawthorne FC (1996a) Infraredspectroscopy of synthetic (NiMgCo)-potassium-richterite InldquoMineral Spectroscopy a tribute to Roger G Burnsrdquo (MDDyar C McCammon and MW Schaefer eds) The Geoche-mical Society Special Publication 5 55-63

Della Ventura G Robert J-L Hawthorne FC Prost R (1996b)Short-range disorder of Si and Ti in the tetrahedral double-chain unit of synthetic Ti-bearing potassium-richterite AmMineral 81 56-60

Della Ventura G Hawthorne FC Robert J-L Delbove FWelch MD Raudsepp M (1999) Short-range order ofcations in synthetic amphiboles along the richterite - pargasitejoin Eur J Mineral 11 79-94

Gaillard F Scaillet B Pichavant M Beacuteny JM (2001) Theeffect of water and fO2 on the ferric-ferrous ratio of silicicmelts Chem Geol 174 255-273

Ginzburg IV (1965) Holmquistite and its structural variant-clino-holmquistite Trudy Min Muz Akad Nauk USSR 16 73-89 (inRussian)

Hamilton DL amp Henderson CMB (1968) The preparation ofsilicate compositions by a gelling method Mineral Mag 36832ndash838

Hawthorne FC (1983) The crystal chemistry of the amphibolesCan Mineral 21 174-481

mdash (1997) Short-range order in amphiboles a bond-valenceapproach Can Mineral 35 201-216

Hawthorne FC Ungaretti L Oberti R Bottazzi P (1993) LiAn important component in igneous alkali amphiboles AmMineral 78 733-745

Hawthorne FC Ungaretti L Oberti R Cannillo E (1994) Themechanism of Li incorporation in amphiboles Am Mineral79 443-451

Hawthorne FC Della Ventura G Robert J-L (1996a) Short-range order of (NaK) and Al in tremolite An infrared studyAm Mineral 81 782-784

Hawthorne FC Della Ventura G Robert J-L (1996b) Short-range order and long-range order in amphiboles A model forthe interpretation of infrared spectra in the principal OH-stretching region In ldquoMineral Spectroscopy a tribute to RogerG Burnsrdquo (MD Dyar C McCammon and MW Schaefereds) The Geochemical Society Special Publication 5 49-54

Hawthorne FC Della Ventura G Robert J-L Welch MDRaudsepp M Jenkins DM (1997) A Rietveld and infraredstudy of synthetic amphiboles along the potassium-richterite -tremolite join Am Mineral 82 708-716

Hawthorne FC Welch MD Della Ventura G Shuangxi LiuRobert J-L Jenkins DM (2000) Short-range order insynthetic aluminous tremolites an infrared and triple-quantumMAS NMR study Am Mineral 85 1716-1724

Hirschmann M Evans BW Yang H (1994) Composition andtemperature dependence of Fe-Mg ordering in cummingtonite-grunerite as determined by X-ray diffraction Am Mineral 79862-877

Irusteta MC amp Whittaker EJW (1975) A three dimensionalrefinement of the structure of holmquistite Acta Cryst B31145-150

Lang G (1963) Interpretation of experimental Moumlssbauer spec-trum areas Nucl Inst and Meth 24 425- 428

Law AD amp Whittaker EJ (1981) Studies of the orthoamphiboles1 ndash The Moumlssbauer and infrared spectra of holmquistite BullMineacuteral 104 381-386

Leake BE Woolley AR Arps CES BirchWD Gilbert MCGrice JD Hawthorne FC Kato A Kisch HJ KrivovichevVG Linthout K Laird J Mandarino JA Maresch WVNickel EH Rock NMS Schumacher JC Smith DCUngaretti L Whittacker EJW Youzhi G (1997)Nomenclature of amphiboles Report of the subcommitte onamphiboles of the International Mineralogical Associationcommission on new minerals and minerals name Eur JMineral 9 623-651

Litvin AL amp Petrunina AA (1975) On the crystal structure ofclinoholmquistite Konst Svoistva Mineral 8 6-8 (in Russian)

Litvin AL Ginzburg IV Egorova LN Ostapenko SS (1973)On the crystal structure of holmquistite Const Prop Mineral7 18-31

London D (1986) Holmquistite as a guide to pegmatitic rare metaldeposits Econ Geol 81 704-712

Long GJ Cranshaw TE Longworth G (1983) The idealMoumlssbauer effect absorber thickness Moumlssbauer Effect DataJournal 6(2) 42-49

Maresch WV amp Langer K (1976) Synthesis lattice constants andOH-valence vibrations of an orthorhombic amphibole withexcess OH in the system Li2O-MgO-SiO2-H2O ContribMineral Petrol 56 27-34

Monier G amp Robert JL (1986) Muscovite solid solutions in thesystem K2O-MgO-FeO-Al2O3-SiO2-H2O an experimentalstudy at 2 kbar PH2O and comparison with natural Li-free whitemicas Mineral Mag 50 257-266

Oberti R Caballero J-M Ottolini L Andres SL Herreros V(2000) Sodic-ferripedrizite a new monoclinic amphibolebridging the magnesium-iron-manganese-lithium and thesodium-calcium group Am Mineral 85 578-585

326

2000) The FTIR OH-spectrum of ferri-clinoferro-holmquistite (Fig 4a) albeit extremely simple can beused to derive useful information based on band multi-plicity and band widths

It is well known that the presence of two cations at theoctahedral sites directly bonded to the hydroxyl groupgives rise to four bands in the infrared OH-stretchingregion which can be assigned to the four possible config-urations (Strens 1966 Hawthorne et al 1996b DellaVentura 1992) The presence of a single band in the spec-trum of ferri-clinoferroholmquistite indicates that there isa single cation at the M1 and M3 sites which in turnimplies ordering of Fe3+ at the M2 site which is not coor-dinated to OH This result is in accord with the X-raysingle-crystal work of Caballero et al (1998) and Obertiet al (2000 2003) which shows that Fe3+ is stronglyordered at the M2 site in all Li-rich amphiboles so farrefined The small band at 3644 cm-1 also conf irms thatoctahedral Li is ordered at either the M1 or the M3 sitesin agreement with all structure refinements done onnatural samples from Pedriza (Caballero et al 1998Oberti et al 2000 2003) or on Li-bearing sodic amphi-boles (Hawthorne et al 1993 1994) which indicate thatCLi is ordered at M3

The presence of different cations at the sites involvedin the absorption is known to give rise to signif icant bandbroadening (ldquosubstitutional broadeningrdquo Strens 1974)Again the spectrum of ferri-clinoferroholmquistite hasvery sharp bands this situation has been found so faronly in tremolite (Fig 4) which is a strongly orderedamphibole (Hawthorne 1997) with an empty A site M4occupied by Ca (plus minor Mg Hawthorne et al 2000and references therein) and the three octahedral sitesoccupied by Mg The local cummingtonite environmentin tremolite gives rise to a well-defined component in thespectrum at 3668 cm-1 (arrowed in Fig 4) Cationdisorder at sites not directly bonded to OH such as thepresence of a cation at the A-site or the Na-Ca disorder atthe NNN M4 site strongly affects the OH-stretchingband width (Hawthorne et al 1997) The very sharpFWHM of the single main band in the spectrum of ferri-clinoferroholmquistite is therefore indicative ofextremely low amounts of Fe2+ at M4 and consequentlyof Li at M3

The local configuration around the OH-group in ferri-clinoferroholmquistite is identical to that in ferroactinoliteie FeFeFe-OH-A -SiSi (notation introduced by DellaVentura et al 1999) On the other hand the wavenumberof this band in ferri-clinoferroholmquistite is 10 cm-1 lowerthan in ferro-actinolite (Fig 5) Changes in cation occu-pancy at the NNN M2 site may also give rise to band split-ting and shift (Della Ventura et al 1999) For example inpargasites and Al-bearing tremolites there is a downwardshift of ~ 20 cm-1 due to the presence of Al at the M2 site(Hawthorne et al 2000) We tentatively attribute the down-ward shift of 10 cm-1 observed in ferri-clinoferroholmquis-tite relative to ferro-actinolite to the NNN effect of Fe3+ atthe M2 site However this point needs further experimentalsupport as cation disorder at M4 can also induce a similarshift

Conclusions

Ferri-clinoferroholmquistite Li2(Fe2+3Fe3+

2)Si8O22(OH)2 has been obtained in a very limited temperaturerange between 500-600degC for a wide pressure range(1-7 kbar) For T sup3 600degC it is replaced by an assemblageof pyroxene + magnetite + quartz These results confirmthe prediction based on petrological observation of Obertiet al (2003) on the upper thermal stability of this type ofLi-rich amphiboles Spectroscopic data show that ferri-clinoferroholmquistite has a strongly ordered cationarrangement in agreement with the prediction ofHawthorne (1997) on local bond-valence ground and withsingle-crystal refinements on Li-rich amphiboles (egCaballero et al 1998 Oberti et al 2000 2003)Moumlssbauer and infrared spectroscopy can be extremelyuseful in characterizing both long-range and short-rangeorder in synthetic phases which cannot be adequately char-acterised by EMP analysis and X-ray structure refinement

Acknowledgements We thank Bruno Di Sabatino forconstructive comments at the beginning of the workAnnibale Mottana and Ciriaco Giampaolo allowed us useof the analytical facilities at the University of Roma TreThanks are due to Sergio Lomastro for assistance in X-ray data collection and to Arnaud Papin Jacques Rouxand Bruno Scaillet for technical assistance duringsynthesis Part of this work was done during the stay of

Synthetic ferri-clinoferroholmquistite 325

Fig 5 The IR OH-stretching spectrum of ferri-clinoferro-holmquistite compared to that of ferro-actinolite (sample MH13Della Ventura unpublished)

G Iezzi G Della Ventura G Pedrazzi J-L Robert R Oberti

GI at ISTO-CNRS (Orleacuteans) financed by theUniversity of Chieti and an EGIDE-Italian ForeignAffairs Ministry fellowships The constructive criticismof referees Walter Maresch and Frank C Hawthorne isalso acknowledged

References

Boffa Ballaran T Angel RJ Carpenter MA (2000) High pres-sure transformation behaviour of the cummingtonite-gruneritesolid-solution Eur J Mineral 12 1195-1213

Boffa Ballaran T Carpenter MA Domeneghetti MC (2001)Phase transition and thermodynamic mixing behaviour of thecummingtonite-grunerite solid-solution Phys ChemMinerals 28 87-101

Caballero J-M Monge A La Iglesia A Tornos F (1998) Ferri-clinoholmquistite Li2(Fe2+Mg)Fe3+

2Si8O22(OH)2 a new BLiclinoamphibole from the Pedriza Massif Sierra deGuadarrama Spanish Central System Am Mineral 83 167-171

Chou IM (1987) Oxygen buffer and hydrogen sensor techniqueat elevated pressures and temperatures In ldquoHydrothermalexperiments techniquesrdquo (HL Barnes amp GC Ulmer eds)Wiley New York

DallrsquoAgnol R Scaillet B Pichavant M (1999) An experimentalstudy of a lower Proterozoic A-type granite from the EasternAmazonian Craton Brazil J Petrol 40 1673-1698

Deer WA Howie RA Zussman J (1999) Rock formingminerals Double-chain Silicates Ed Longman Scientific ampTechnical pp 692

Della Ventura G (1992) Recent developments in the synthesis andcharacterization of amphiboles Synthesis and crystal-chem-istry of richterites Trends in Mineralogy 1 153-192

Della Ventura G Robert JL Hawthorne FC (1996a) Infraredspectroscopy of synthetic (NiMgCo)-potassium-richterite InldquoMineral Spectroscopy a tribute to Roger G Burnsrdquo (MDDyar C McCammon and MW Schaefer eds) The Geoche-mical Society Special Publication 5 55-63

Della Ventura G Robert J-L Hawthorne FC Prost R (1996b)Short-range disorder of Si and Ti in the tetrahedral double-chain unit of synthetic Ti-bearing potassium-richterite AmMineral 81 56-60

Della Ventura G Hawthorne FC Robert J-L Delbove FWelch MD Raudsepp M (1999) Short-range order ofcations in synthetic amphiboles along the richterite - pargasitejoin Eur J Mineral 11 79-94

Gaillard F Scaillet B Pichavant M Beacuteny JM (2001) Theeffect of water and fO2 on the ferric-ferrous ratio of silicicmelts Chem Geol 174 255-273

Ginzburg IV (1965) Holmquistite and its structural variant-clino-holmquistite Trudy Min Muz Akad Nauk USSR 16 73-89 (inRussian)

Hamilton DL amp Henderson CMB (1968) The preparation ofsilicate compositions by a gelling method Mineral Mag 36832ndash838

Hawthorne FC (1983) The crystal chemistry of the amphibolesCan Mineral 21 174-481

mdash (1997) Short-range order in amphiboles a bond-valenceapproach Can Mineral 35 201-216

Hawthorne FC Ungaretti L Oberti R Bottazzi P (1993) LiAn important component in igneous alkali amphiboles AmMineral 78 733-745

Hawthorne FC Ungaretti L Oberti R Cannillo E (1994) Themechanism of Li incorporation in amphiboles Am Mineral79 443-451

Hawthorne FC Della Ventura G Robert J-L (1996a) Short-range order of (NaK) and Al in tremolite An infrared studyAm Mineral 81 782-784

Hawthorne FC Della Ventura G Robert J-L (1996b) Short-range order and long-range order in amphiboles A model forthe interpretation of infrared spectra in the principal OH-stretching region In ldquoMineral Spectroscopy a tribute to RogerG Burnsrdquo (MD Dyar C McCammon and MW Schaefereds) The Geochemical Society Special Publication 5 49-54

Hawthorne FC Della Ventura G Robert J-L Welch MDRaudsepp M Jenkins DM (1997) A Rietveld and infraredstudy of synthetic amphiboles along the potassium-richterite -tremolite join Am Mineral 82 708-716

Hawthorne FC Welch MD Della Ventura G Shuangxi LiuRobert J-L Jenkins DM (2000) Short-range order insynthetic aluminous tremolites an infrared and triple-quantumMAS NMR study Am Mineral 85 1716-1724

Hirschmann M Evans BW Yang H (1994) Composition andtemperature dependence of Fe-Mg ordering in cummingtonite-grunerite as determined by X-ray diffraction Am Mineral 79862-877

Irusteta MC amp Whittaker EJW (1975) A three dimensionalrefinement of the structure of holmquistite Acta Cryst B31145-150

Lang G (1963) Interpretation of experimental Moumlssbauer spec-trum areas Nucl Inst and Meth 24 425- 428

Law AD amp Whittaker EJ (1981) Studies of the orthoamphiboles1 ndash The Moumlssbauer and infrared spectra of holmquistite BullMineacuteral 104 381-386

Leake BE Woolley AR Arps CES BirchWD Gilbert MCGrice JD Hawthorne FC Kato A Kisch HJ KrivovichevVG Linthout K Laird J Mandarino JA Maresch WVNickel EH Rock NMS Schumacher JC Smith DCUngaretti L Whittacker EJW Youzhi G (1997)Nomenclature of amphiboles Report of the subcommitte onamphiboles of the International Mineralogical Associationcommission on new minerals and minerals name Eur JMineral 9 623-651

Litvin AL amp Petrunina AA (1975) On the crystal structure ofclinoholmquistite Konst Svoistva Mineral 8 6-8 (in Russian)

Litvin AL Ginzburg IV Egorova LN Ostapenko SS (1973)On the crystal structure of holmquistite Const Prop Mineral7 18-31

London D (1986) Holmquistite as a guide to pegmatitic rare metaldeposits Econ Geol 81 704-712

Long GJ Cranshaw TE Longworth G (1983) The idealMoumlssbauer effect absorber thickness Moumlssbauer Effect DataJournal 6(2) 42-49

Maresch WV amp Langer K (1976) Synthesis lattice constants andOH-valence vibrations of an orthorhombic amphibole withexcess OH in the system Li2O-MgO-SiO2-H2O ContribMineral Petrol 56 27-34

Monier G amp Robert JL (1986) Muscovite solid solutions in thesystem K2O-MgO-FeO-Al2O3-SiO2-H2O an experimentalstudy at 2 kbar PH2O and comparison with natural Li-free whitemicas Mineral Mag 50 257-266

Oberti R Caballero J-M Ottolini L Andres SL Herreros V(2000) Sodic-ferripedrizite a new monoclinic amphibolebridging the magnesium-iron-manganese-lithium and thesodium-calcium group Am Mineral 85 578-585

326

G Iezzi G Della Ventura G Pedrazzi J-L Robert R Oberti

GI at ISTO-CNRS (Orleacuteans) financed by theUniversity of Chieti and an EGIDE-Italian ForeignAffairs Ministry fellowships The constructive criticismof referees Walter Maresch and Frank C Hawthorne isalso acknowledged

References

Boffa Ballaran T Angel RJ Carpenter MA (2000) High pres-sure transformation behaviour of the cummingtonite-gruneritesolid-solution Eur J Mineral 12 1195-1213

Boffa Ballaran T Carpenter MA Domeneghetti MC (2001)Phase transition and thermodynamic mixing behaviour of thecummingtonite-grunerite solid-solution Phys ChemMinerals 28 87-101

Caballero J-M Monge A La Iglesia A Tornos F (1998) Ferri-clinoholmquistite Li2(Fe2+Mg)Fe3+

2Si8O22(OH)2 a new BLiclinoamphibole from the Pedriza Massif Sierra deGuadarrama Spanish Central System Am Mineral 83 167-171

Chou IM (1987) Oxygen buffer and hydrogen sensor techniqueat elevated pressures and temperatures In ldquoHydrothermalexperiments techniquesrdquo (HL Barnes amp GC Ulmer eds)Wiley New York

DallrsquoAgnol R Scaillet B Pichavant M (1999) An experimentalstudy of a lower Proterozoic A-type granite from the EasternAmazonian Craton Brazil J Petrol 40 1673-1698

Deer WA Howie RA Zussman J (1999) Rock formingminerals Double-chain Silicates Ed Longman Scientific ampTechnical pp 692

Della Ventura G (1992) Recent developments in the synthesis andcharacterization of amphiboles Synthesis and crystal-chem-istry of richterites Trends in Mineralogy 1 153-192

Della Ventura G Robert JL Hawthorne FC (1996a) Infraredspectroscopy of synthetic (NiMgCo)-potassium-richterite InldquoMineral Spectroscopy a tribute to Roger G Burnsrdquo (MDDyar C McCammon and MW Schaefer eds) The Geoche-mical Society Special Publication 5 55-63

Della Ventura G Robert J-L Hawthorne FC Prost R (1996b)Short-range disorder of Si and Ti in the tetrahedral double-chain unit of synthetic Ti-bearing potassium-richterite AmMineral 81 56-60

Della Ventura G Hawthorne FC Robert J-L Delbove FWelch MD Raudsepp M (1999) Short-range order ofcations in synthetic amphiboles along the richterite - pargasitejoin Eur J Mineral 11 79-94

Gaillard F Scaillet B Pichavant M Beacuteny JM (2001) Theeffect of water and fO2 on the ferric-ferrous ratio of silicicmelts Chem Geol 174 255-273

Ginzburg IV (1965) Holmquistite and its structural variant-clino-holmquistite Trudy Min Muz Akad Nauk USSR 16 73-89 (inRussian)

Hamilton DL amp Henderson CMB (1968) The preparation ofsilicate compositions by a gelling method Mineral Mag 36832ndash838

Hawthorne FC (1983) The crystal chemistry of the amphibolesCan Mineral 21 174-481

mdash (1997) Short-range order in amphiboles a bond-valenceapproach Can Mineral 35 201-216

Hawthorne FC Ungaretti L Oberti R Bottazzi P (1993) LiAn important component in igneous alkali amphiboles AmMineral 78 733-745

Hawthorne FC Ungaretti L Oberti R Cannillo E (1994) Themechanism of Li incorporation in amphiboles Am Mineral79 443-451

Hawthorne FC Della Ventura G Robert J-L (1996a) Short-range order of (NaK) and Al in tremolite An infrared studyAm Mineral 81 782-784

Hawthorne FC Della Ventura G Robert J-L (1996b) Short-range order and long-range order in amphiboles A model forthe interpretation of infrared spectra in the principal OH-stretching region In ldquoMineral Spectroscopy a tribute to RogerG Burnsrdquo (MD Dyar C McCammon and MW Schaefereds) The Geochemical Society Special Publication 5 49-54

Hawthorne FC Della Ventura G Robert J-L Welch MDRaudsepp M Jenkins DM (1997) A Rietveld and infraredstudy of synthetic amphiboles along the potassium-richterite -tremolite join Am Mineral 82 708-716

Hawthorne FC Welch MD Della Ventura G Shuangxi LiuRobert J-L Jenkins DM (2000) Short-range order insynthetic aluminous tremolites an infrared and triple-quantumMAS NMR study Am Mineral 85 1716-1724

Hirschmann M Evans BW Yang H (1994) Composition andtemperature dependence of Fe-Mg ordering in cummingtonite-grunerite as determined by X-ray diffraction Am Mineral 79862-877

Irusteta MC amp Whittaker EJW (1975) A three dimensionalrefinement of the structure of holmquistite Acta Cryst B31145-150

Lang G (1963) Interpretation of experimental Moumlssbauer spec-trum areas Nucl Inst and Meth 24 425- 428

Law AD amp Whittaker EJ (1981) Studies of the orthoamphiboles1 ndash The Moumlssbauer and infrared spectra of holmquistite BullMineacuteral 104 381-386

Leake BE Woolley AR Arps CES BirchWD Gilbert MCGrice JD Hawthorne FC Kato A Kisch HJ KrivovichevVG Linthout K Laird J Mandarino JA Maresch WVNickel EH Rock NMS Schumacher JC Smith DCUngaretti L Whittacker EJW Youzhi G (1997)Nomenclature of amphiboles Report of the subcommitte onamphiboles of the International Mineralogical Associationcommission on new minerals and minerals name Eur JMineral 9 623-651

Litvin AL amp Petrunina AA (1975) On the crystal structure ofclinoholmquistite Konst Svoistva Mineral 8 6-8 (in Russian)

Litvin AL Ginzburg IV Egorova LN Ostapenko SS (1973)On the crystal structure of holmquistite Const Prop Mineral7 18-31

London D (1986) Holmquistite as a guide to pegmatitic rare metaldeposits Econ Geol 81 704-712

Long GJ Cranshaw TE Longworth G (1983) The idealMoumlssbauer effect absorber thickness Moumlssbauer Effect DataJournal 6(2) 42-49

Maresch WV amp Langer K (1976) Synthesis lattice constants andOH-valence vibrations of an orthorhombic amphibole withexcess OH in the system Li2O-MgO-SiO2-H2O ContribMineral Petrol 56 27-34

Monier G amp Robert JL (1986) Muscovite solid solutions in thesystem K2O-MgO-FeO-Al2O3-SiO2-H2O an experimentalstudy at 2 kbar PH2O and comparison with natural Li-free whitemicas Mineral Mag 50 257-266

Oberti R Caballero J-M Ottolini L Andres SL Herreros V(2000) Sodic-ferripedrizite a new monoclinic amphibolebridging the magnesium-iron-manganese-lithium and thesodium-calcium group Am Mineral 85 578-585

326

Oberti R Caacutemara F Ottolini L Caballero JM (2003) Lithiumin amphiboles detection quantification incorporation mecha-nisms and nomenclature in the compositional space bridgingsodic and BLi amphiboles Eur J Mineral 15 309-319

Pedrazzi G Cai SZ Ortalli I (1999) Evaluation of experi-mental data lineshape and goodness of fit In ldquoMoumlssbauerSpectroscopy in Material Sciencesrdquo (Miglierini and Petridiseds) Kluwer Academic Publisher 373-384

Rancourt DG (1989) Accurate site population from Moumlssbauerspectroscopy Nucl Inst and Meth B44 199-210

Rancourt DG McDonald AM Lalonde AE Ping JY (1993)Moumlssbauer absorber thickness for accurate site population inFe-bearing minerals Am Mineral 78 1-7

Robert JL Della Ventura G Thauvin J-L (1989a) The infraredOH-stretching region of synthetic richterites in the systemNa2O-K2O-CaO-MgO-SiO2-H2O-HF Eur J Mineral 1203-211

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Schmidt BC Holtz F Scaillet B Pichavant M (1997) Theinfluence of H2O-H2 fluids and redox conditions on meltingtemperatures in the haplogranite system Contrib MineralPetrol 126 386-400

Strens RGJ (1966) Infrared study of cation ordering and clus-tering in some (FeMg) amphibole solid solutions ChemComm 15 519-520

mdash (1974) The common chain ribbon and ring silicates In ldquoTheInfrared Spectra of Mineralsrdquo (VC Farmer ed) Mineral SocMonogr 4 305-330

Yang H amp Hirschmann MM (1995) Crystal structure of P21mferromagnesian amphibole and the role of cation ordering andcomposition in the P21m reg C2m transition in cummingtoniteAm Mineral 80 916-922

Yang H Hazen RM Prewitt CT Finger LW Lu R HemleyRJ (1998) High-pressure single-crystal X-ray diffraction andinfrared spectroscopic studies of the C2m reg P21m phase tran-sition in cummingtonite Am Mineral 83 288-299

Wiles DB amp Young PA (1981) A new computer program forRietveld analysis of X-ray powder diffraction patterns J ApplCryst 14 149-151

Whittaker EJW (1969) The structure of the orthorhombic amphi-bole holmquistite Acta Cryst B25 394-397

Received 11 February 2002Modified version received 30 July 2002Accepted 3 October 2002

Synthetic ferri-clinoferroholmquistite 327