Synthesis and Fluorine.Hydfoxyl Exchange in the Amblygonite Series

Caiwdian Mineralogist Vol. 14, pp. 357-363 (1976)

SYNTHESISAND FLUORINE.HYDFOXYLEXCHANGE IN THE AMBLYGONITESERIES

SPENCER E. LOH,|, ^rxn WLLIAM S. WISE Departmentof Geologicalsciences, university of california, santa Barbara, ca 9|106

ABSTRACT Souurernr,

The amblygonite series includes the solid solution La s6rieamblygonite consiste en une solution solide between the end members, amblygonite, LiAIPO;F, entre les p6les extr6mes,I'amblygonite (LiAlpO4F) and montebrasite, LiAIPO4OH. The moit comrrion et la mont6brasite (LiAIPO4OH). La compositionla composition range. is between Ambl6 and Amb5o, plus courante que I'on retrouve dans les pqmatites where this series occurs in Li-rich pegmatites. . richesen Li se situe entre Amble et Ambrol Ih com- The end members and four intermediate composi- positions limifss st quatre compositions interm6_ tions were synthesized by standard hydrothermal diaires ont 6t6 synttr6tis6espar voie hydrothermale d tochniques at 600'C and 2 kbar water pressure. All 6@'C et 2 kbar de pressiond'eau. Tous les six para_ six ell param€ters vary linearly across the com- mdtresde l4 maills varient de fagon linGaire. positional I-es ai_ range. Amblygonite cell dimensions arg mensionsde la maille de I'amblygonite sont, a 8.103, a p 5.103, b 7.221, c 5.5064, a L14"22" 98.54'. b7.22L,c 5.506[, aLl422t, p 98.b4',^y 6ZTfz'iww t 67'02'; and montebrasite, a 5.185, b 7.161, c mont6brasite,a 5.185,b Z.t6I, c 5.OOA, 5.040A, a ll2"I8" B 97"51" .t 67"52'. These !t c 112"18r, cell P 97%It, Les paramOtresae cescomposGs dimensions indicate that the unit cells of the pure purement!.97"52'. Li litliques sont un peu plus petits que-ceux series are slightly smaller than those of the des natural min6raux naturels. Les indices de r6-fraction mineral se.ries. Refractive indices are €ssen- coincident tially identical essentiellementavec ceux des min6raux with comparable natural minsrals. naturels. Les Equilibrium compositions compositions d'6quilibre de la phase . of ttre amblygonite phase amblygonite dans la r6action in the exchange reaction : d'6changeLiAlirO4F LiAlpO4F + ffrb *HzO:LiAIPO+OH*HF ont LiAIPO4OH $ HF were approached 6t6 ipproch6s des from both sides, deux c0t6s i faide des membres extrbmes using pure synthetic end members as starting syntl6- ma- tiques purs commemat6riaux de d6part. Les compo- terials. Gas compositions were controlled bi solid gazeuses The sitions ont 6t6 contr6l6espar des solutions F"flg=. results, z6-5 for several levels of Jnr, can tamponssolides. the equilibrium Les r6sultats,,Aab pour les diff€rents F"jl^t" constant in the fonn, log niveaux de/gp, peuvent K.-319:' : 4.58 (+O.22) : (Jnr/uzo) 6tre adaptdsd la constanre : los + log d'6quilibrep{ log Klongff: -4.58 (+0.22) : [(l - re*),/ra-rl which allorrs calculation gas loc of Ay/Ia2Q * loe - ,cA-)/ra^b] ce qui permet compositions for natural amblygonite compositions [(1 le calcul gazeusespour les-composi- beyond therangeof tJrebuffers. If AGIAZ' 0 and -des_compositions LG,/L P 5O, tions d'amblygonitesnaturelles au deli des soluiions as in the LiF-LiOH exchangereaction, tampons. Si :a thenlog I( : - f000/?("K). AG"/AI 0 et LG"/LP = 0, comme dans la r6action d'6change : - Equilibrium constants at pegmatitic alors log K OCf/ temperatures ?('K). Les constantesd'6quilibre, are very small, indicating strong i dis temp6ratures fractionation of pegmatitiques, sont trds petites indiquant F into-the amblygonite phase. Isothermal ainsi un crystalliza- fractionnementde F dans la phaseamblygonite. tion of amblygonite will cause a decrease in La tle f cristallisation isothermique de I'amblygonite abais- content of the gas, and crystal zoning will be toward montebrasite sera le contenu en F du gls, et la zor^;tlondu cristal compositions. Znung with increases sera dans of F content la direction d'une augmentationen mont6- result from (l) increases in fo, ac_ brasite.Une zonationqui comFanying increases in gas pressure d6montreune augmentation caused by en F r6sultera (1) d'une haussesen qui silicate phase crystallization and/or (2) /rc,, ac@m- by decreas_ pagne I'augmentation de la pressiongazeuse caus6e ing temperature leading to smaller' e[uilibrium par constants. la cristallisation de silicates et/oa (2) d'un abais- sement de la temp6rature menant i des constantes d'6quilibre plus petites. (fraduit par le journal)

INTRoDUCTToN

'rPresent Arnblygonite series address: Department of Geological polytechnic Sciences, Virginia Institute & State A continuous, isomorphous series exists be- Univ., Blacksbury, VA 24061. tween the end members,amblygonite, LiAlpO4F, 357 358 TTIE CANADIAN MINERALOGIST

mole o/o F 40 60

vt o(, c E (,5 (, a o C' c

wt. 7o F Frc. 1. Histogram of the compositions of natural memben of the ambly' gonite series from data compiled by Loh (1975). and montebrasite, LiAIPOcOH. Genqrally, the Ginzburg 1950; Gallaghet 1967; Connolly & name amblygonite or amblygonite series has O'Hara fgZg; ff"i*ich & Corey 1955; Cern6 been used to representany member of the series. et al- 1972). Neither pure amblygonite nor montebrasite has C,ern6et al. (1973) presenteddetailed physicat The highest reported been found in nature., properties on twenty analyzed latural -ambly- mole %) fluorine content is 11.8 vtt. Vo Q2 lonite minerals. Specific gravities, -refractive from Saxony (Moss ef aI. 1969) and the lowest indices, and differential thermal behavior all is 0.85 wt. % Q mole Vo) from Siberia (Vlasov show gradual changes with F-content. X-ray 1966). Figure 1 illustrates the compositions of powdei diffraction methods provide- efftcient all the reported occurrences of amblygonite and ind accurate means for the indirect determina- montebrasite, 80Vo of which have less than tion of F content. T:he 2A(CuKa') values for the 50 mole Vo fluoine. Sodium is the most com- (131) reflection (Moss et aL 1969) shory line.ar mon minor element replacing lithium, in changes with the fluorine content in amblygonite amounts averaging near 0.5 mole Vo. mineials. The determination line was refined by The members of tlis series occur chiefly in eernd et al. (1973). lithium- and phosphate-rich granitic pesmatites, commonly as ellipsoidal nodules or crude crys- Purpose of the studY tals up to 0.5 m in a paragenesissimilar to that has been done of spodumene(Moore 1973). The perfect {100} Since little experimental work cleavage and milky-white colot often lead to on this minglal-ssrigs, pure end members and confusion with the feldspars. The minerals most intermediate members of the amblygonite series commonly associated with amblygonite a,re have been synthesized to investigate some of spodumene, apatite, lepidolite, tourmaline, and the physical properties and to test the complete- other lithium phosphate minerals. Amblygonite o.r. of th" solid solution. Comparison of proper' has also been found in high-tempetature veins ties of the synthetic and natural minerals will and greisen with cassiteriteo topz, and mica. help to further define the mineral series espe- The minerals of the amblygonite series have ciaily for the end members. More important is been found at the famous pegmatite localities the determination of the relationship between of Varutrask, Sweden; Karakhstan and Siberia, the F content of the amblygonite and the lm of USSR; Montebraso France; Rhodesia; Black the pegmatite magma. In this paper we p,resent Hills, South Dakota, Eight Mile Park, Colorado; the properties of a series of synthetic amblygon- Pala, California; Newry, Hebron, Buckfield, ites.-and we show that most amblygonites crys- and other localities in Maine; and Tanco Peg- tallize from fluids with very low lr-less tlan matite, Bernic Lake, Manitoba (Quensel 1956; 0.005 bars. SYNTHESIS OF TIIE AMBLYCONITE SERIES 359

TABLEl. CoMPUTEDoENSITIES, CELL DII4ENSIoNS, Cu{dl(131) At'lDMEASURE0 I-REFRACTM INDEX 0F SYNTHETIC AMBLYGONITE,MONTEBM5ITE, AND lTS INTERMIDIA1EI.{EMBER5L nnt amb20 amb40 amb6o ambgo amb

a (i) 5.r85(6) 5.r75(?) 5.r67(r) 5.r5l (3) 5.134(2) 5.130(3) b (i) 7.r6r (e) 7.164(21 7.r7r (3) 7.175(6) 7.213(6') 7.221 (5\ c (i) 5.o4o (5) 5.042(2) 5.047(2) 5.045(4) 5.056(3) 5.056(4)

o ll2" 18(6)' 112.37(2), il2.57(2), r13023(4)', r14" 3(4)', 1r4. 22(4)', 6 97'5l(8)' e8' o(2)' e8" 3(2), e8" r5(4)' e8" 42(41' e8. 54(5)' 't2(2)' | 67.5217)' 67o 46(21', 67" 42(z)' 67" 30(3)' 67. 67" 2(3)'

v (i)3 roo.q(z) 15e.8(6) 15e.3(7) 158.1(r) 157.6(r) 157.r(r) densitv (caIc.J r'uzu 3.041 3.058 3.089 3.108 3.t 26

i;i;:i' 52.22" 52.42" 52.58" 52.84" 53.07. 53.23' i:ll:ll 52.23" 52.40. 52.57" 52.85" 53.07" 53.?4" 1-index 1.643 (l) 1.634 (l) 1.622 (1) 1.612 (l) 1.603 (l) 1.592(1)

SyNtnnsrs or Mntvtusns oF THE Complete X-ray powder patternsz were ob- AMBLycoNrrn SrnIEs tained for each composition, and the unit-cell using the U.S. Geolo- Experimental procedure dimensions were refined gical Survey's FORTRAN IV computer pro- The end members and four intermediate gram W7214 (see Table 1). Linear regxessions compositions of the amblygonite series were of each parameter are given in Table 2 with prepared from mixes of the proper proportions the compositions expressedboth as mole Vo F of LiF, LiOH.HIO, and AlPOa.l Approximately and wt. 7o F, which may be compared directly 30 mg of mix and 15 mg of water were sealed to those developed by Cern6 et aI. (1973). The in 2 cm long and 3 mm diameter gold tubes. values of 20(l3L) for each composition and The synthesizingruns were conducted at 600"C and 2000 bars water pressure in standard, ex- 2Copies ternally heated, cold-sealpressure vessels.Tem- available from the authors. peratures were regulated to within +3o, and pressureto within -r10 bars. These runs yielded TABLE2. REGRESSIONEOUATIONS AND CORRELATION COEFFICTENTS OF approximately 30 mg of fine-grained crystalline MEASUREDPAMIIETERS OF A SYNTHETICI.IOT.ITEBMSITE-AI'IBLYGONITE SERIES aggregates,which were identified by X-ray dif- equation I fraction and optical means. Run times of one 20r3rcuKot(meas.)(') = 0.0104 x F mole%+ 52.208 (.998) week were sufficient to allow the lithium to react 20131CuKc1(reas.)(')= 0.0807x Fgg.f + 52.208 (.998) with all of the AlPOa. a (fi) - -0.00059x F mtez + 5.187 (.9s9) Physical properties of the amblygonite sertes a(fr) --o.ooa6 x Frt.% + 5.187 (.989) The synthetic crystals are yery small (-1 pm), b (l) . o.ooooqx F mlez + 7.152 (.s26) = + (.926) but appear to have homogeneouscompositions, b(A) 0.0050x Falh% 7.152 based on the sharpness of X-ray reflections. c 1i1 = g.g6r'lt x F rclez + 5.039 (.93r) = q.6p'1a X-ray powder diffraction charts were obtained c1i1 x Fwr.U + 5.039 (.93t) (') . 0.0215x F nolez + 112.20 (.992) by scanning at /2"/minute and using Si as an " external standard. The refractive index v was a (') = 0.1676 x F wt. + 112.20 (,9921 mea$ured by the Becke method in cafi6rated B (") . 0.0108 x F mleg + 97.75 (.964) oils. The highest index of the synthetic crystals B(.) " 0.0840x Fwt.% + 97.75 (.964) showing the highest birefringence was measured. 1 (') = -0.0086 x Fmolez a 67.93 (.981) y (") . -0.0672 x F vl. + 67.93 (.981)

v (i)3. -0.0345 x F mleg + 160.4 (.991) rLiF and LiOH.HTO are reagert-grade stock items; v{i13"-9.2*t x Fwt.u + 160.4 (.991) AIPOa was prepared by reaction of reagent-grade Al wire with diluted phosphoric acid anal heating r-index =-0.00051x Frc]ez + 1.643 (.999) the precipitate for 24 hours at 600'C. y-index.-0.00378x Frt.g + 1.643 (.999) 360 TTIE CANADIAN MINERALOGIST regression constants are rePorted in Tables I pressure.With each buffer, both synthetic mon- and 2. Densities were calculated from the unit- iebrasite and amblygonite were allowed to cell volumes and ideal-member compositions. equilibrate with each buffered gas composition. The maximum refractive index, y, varies along Run times of four weeks were necessaryfor the a line almost identical with that of eetnd et al. solids to approach the equilibrium composition. (1973). The buffer-charge arrangement was similar to The cell lengths and 2f,Q3l) reflect unit-cell that of Munoz & Eugster (1969) except that the volumes that are 0.3 to O.4Vo smaller than charge was separated from the buffer by Au corresponding natural minerals. Most natural foil disks; the wrapped packet for the charge amblygonites contain small amounts of Na and used by Munoz & Eugster proved too difficult Ca that probably account for the larger spacings. for complete gas exchange. Since the refractive indices of the synthetic and Since most natural amblygonitescontain small natural minerals are essentially the same, the amounts of Ca and Na, it is to be expectedthat Na and Ca substitution must have little effect the synthetic amblygonite will not only equili- on thesevalues. brate with the gas but also with the feldspar of the buffer and accept small amounts of Na or Ca into its structure. The F content of the FLuonrNe-HYDRoxYLExcnlNcn equilibrated amblygonites was estimated from the refractive index, which is essentially inde- Experimental methods pendent of the Na and Ca content. Measure- ments of 20(131) do not give concordant com- The exchange between a solid phase of the positions, if the line for synthetic members is gas amblygonite series and an F-bearing can used. However, concordant compositions (esti- be expressedby the reaction: amblygonite+Hro mated accuracy is i2 mole Vo) are obtained : montebrasite+HF, for which the equilibrium from the 2f,{031)line for natural minerals, clear- constant is ly indicating compositions closely corresponding minerals. Jn ' a.^t .) to natural rI are presented in Table 4 and plotted ae^v Run data Ir.2o' on Figure 2. Even though the resulting com- The exchangewas studied by the buffer tech- positions are all F-rich, we believe that-a-mean- nique of Munoz & Eugster (L969), in which the ingful curve, relating the F-content of the gas solid is allowed to equilibrate with a fixed, and the amblygonite, can be drawn through buffered gas composition. In this study the ex' these points. change was studied at a single temperature properties based on the (600'C:L10") and at 2000 bars vapor pressure. Thermodynamic experimental results The frn in the gas was buffered by the as- semblages By assumingthat the mole fraction of ambly- wollastonite-fluorite-quartz (WFQ) gonite (re-r) is equal to the activity of ambly- andalusite-fluorite-anorthite-quartz (AFAQ) andalusite-villiamite-albite-qvartz (AVAQ)' TABLE4. RUNDATA FOR SYNTHETIC AMBLYGONITES ANOMONTE- In order to spread the range further, the hy- BRASITESEQUILIBRATED I.IITH gUFFERED H-O-F GASES drogen hematite-magnetite (IIM) was combined Run ';:i: '("ryt with the fluorine buffers (see Munoz & Eugster No. Burrers iiiiii rll$, *i * 1969). Table 3 lists the buffer assemblagesand (HM)(l^lFQ) otz on calculated fugacities in the O-H-F gas controlled 199 M 600(4) '149 95 by the buffers at 60O'e and 2 kbar total gas A (Hr'1)(l,rFQ) 5e3(',I) 610 214 M (HM)(AFAQ) 600(5) 64tl 90 2?1 A (HM)(AFAq) 600(5) 630 oo TABLE3. CALCULATEDFUGACITIES AND PARTIAL PRESSURES IN O-H-F GASSYSTEM AT 6OO"CAI\ID 2OOO BARS TOTAL PRESSURE 215 M (HM)(AVAq) 600(s) z 64fl 100 FORSIX ASSEMEIAGES. 218 A (HM)(AvAq) 600(5) a 648 r00 'loq 183 M (QFr) (llrFQ) 5e5(3) a 334 77 Buffer -ntf.,- - log fH2 log f^ loq't f- log PHI 'I n2v w2 50 A (QFr) (!lFQ) 5e5(2) z 610 (AvAq) +1.482 1 n)A +l.l90 217 M (QFI)(AFAQ)600(s) a 648 95 (AFAQ)-0.213 3.029 -u.5uc 222 A (QFr)(AFAQ)600(5) 2 630 90 (!rrq) -0.814 3.029 -l.106 216 M (QFr) (AVAQ)600(5) a 648 100 (QFr (AVAQ) 744 97 Hr'l)(AVAQ) +l .581 3.024 -2.257 -27.84 +l.289 219 A ) 600(5,) l,rM)(ArAQ) :0.098 a ita -5l.zl -0.390 r Starting nraterial: M - synthetic montebrasite; -4.1?5 -0.938 Hir)(l,l|rQ ) -0.646 3.028 IJ.JJ -32.30 A = synthetic amblYgonite SYNTHESIS OF THE AMBLYGONITE SERIES 36r gonite (ae-r), an expression of the equilibrium Buffer constant can be obtained. From (1)

1 4 -(AVAuHM) f,.- :---:]]@...... -YAUAO) log- K : log-Jszo * log- (2) +1.O *L Xd^t Using the relation, j, : . where is the fr 2r, I lt fugacity of gas i in the gas mixture, f, is the I fugacity of pure i at the sameP and f, and ncl 2r (D is the partial pressureof f in the mixture, we -AFAOHM) o - obtain AFAA) /fo -(wFouM) ++ -1.O -, '"x,^_ f.". - (wFO + log K : log/Ti p;

1-+ + los (3) Xl'^a J -2.O 100 At 600'C and 2 kbar the value for from fi- o/" F Burnham et al. iL969)is 1046bars, andfnr from mole the reducedvariable chart of Hougen & Watson Fro. 2. Plot of the experimentally determined com- (1946) is 3920 bars. A value for log K was cal- positions of arnblygonite as equilibrated with culated for eachpair of experimentalpoints. An buffered gas phase at 600'C and 2000 bars total average value of -4.58 with a standard de- gas pressrue. Buffers are shown along left edge. viation of.0.22was obtained. The curve Gas compositions are given in Table 3 and experimental data in Table 4. kft-pointing arrows logK : - 4.58(+.22) : .574+ los represent $tading amblygoni0e material; right- pointing arrows, montebrasite. The length of the Al arrows represents the probable error in the com- *q + loe :.jl*!-, !.... (4) Pn o Ie,* position determination. with the standard deviation limilg 641 6..t plotted through the experimental points on Figure 3. The free energy for the exchange reastion at 600"C calculated from 46"too"c = -RZlnK = 18.3(-r9.9X..1. : - Since AGfoo" AGr,"o, + AGr,rrF AG,*o l{ - AGrrnro, substitution of the free energy for a. HrO (Burnham et al. L969), and for HF (Stull Oi & Prophet L970) yields the difference between o the free energies of the two end members AGn*oo - AGr,e-r : 37.0 kcal. (This value is about 8 kcal lower than AGr,",o" - AG1,"," at the same temperature). Even though there are no thermodynamic data on the amblygonite end members, the AG" of the exchange reaction as a function of temperature may be modeled after the LiF+IIzO * LiOH+HF reaction, because bonding in these compounds is similar to that in the amblygonite series. Using the free energies (in stull & Prophet l97O),the A G, of rhe LiF-LioH xa^o reaction is essentiallyconstant over the temperature range of 400' to 700oC. This is because Ftc. 3. Equilibrium-constant curve drawn through experimental points. The dashed curves illustrate the net change in entropy of the reactants and product the variation of. !0.22 in the log value of K. The is nearly zero, for the exchange takes 500' and 450" curves were calculated as ex- place with no breaking and forming new kinds plained in the text. Arrow symbols are the same of bonds. Assuming that the AG, of the ambly- as in Figure 2. 362 THE cANADTAN MINERALOGIST gonite-montebrasite exchange reaction is also gas. After another temperature decrease with nearly constant, an expression relating the gas pressures up, higher amounts of F enter equilibrium constant as a function of tempera- the amblygonite and again zone toward decreas- ture can be calculated from AG, = -R71nK. ing amounts as HF is removed from the gas Substituting values for AG" and R, we obtain phase. log K = 4000/T("K). This expression allows The late montebrasite veining is a result of the calculation of a curve relating ra-r with the solid amblygonite re-equilibrating with the Psr ?.1any temperature. Two such curyes were late-stage gas phase. Crystallization of other calculated for temperatures of 500o and 450"C, F-bearing phases,such as apatite or lepidolite, and are plotted on Figure 3. will further deplete the IIF in the gas. Since apatites and amblygonite have about the same Application of experimental results exchangereaction free energies,there will be no one of the The relationships developed in the preceding particular partitioning of F by either sec- section, illustrated in Figure 3, allow interpreta- minerals. It would appear that the F-poor commonly asso- tions of the crystallization and zoning of ambly- ondary montebrasite and the p. gonites. Three processesleading to composition ciated fluorapatite (Cerni et aI. 1972, 658) changes are: did not equilibrate. in pegmatites, in 1. Isothermal crystallization in a closed sys- Lepidolites crystallizing has been re- tem depletes the gas with respect to F and which earlier-formed amblygonite compositional salsss sqning in the amblygonite with decreas- moving F, will necessarily have contain ing F. The simultaneous crystallization of other restrictions. Commonly, amblygonites which means F-bearing phases, sush as micas, will only ac- less than 50 mole % F ./fig, 1), gas phase prr less than 0.0058 celerate the depletion of F in the gas. that the will have 0.0003 2. Crystallization associated with decreasing bar at 600oC. 0.0010 bar at 500oC, and the temperafure in an open or very large system bar at 450"C. These values are all below (Munoz will lead to substantial increases if F content lower stability of trilithionitefquartz in the amblygonite. In this situation the fugacity r97t). of HF is held constant; other F-bearing phases will have no effect on the composition the of AcKNowLEDGEMENTS amblygonite. 3. Coupled with a temperature decreasewill Acknowledgement is made to the donors of be the crystallization phases of the silicate from The Petroleum Research Fund, administered by the pegmatite increasing gas pressure the and the American Chemical Society, for support of also the fugacity of I{F higher which will lead to this research. The Research Committee of the F contents in tle amblygonite. The degree of Univerrity of California, Santa Barbara, made increase, of course, will depend on how much funds available for early stages of the research F is removed by other minerals. and for computer reduction of X-ray data. These processescan be applied to the compositional changes in amblygonites in the Tanco Pegmatite at Bernic Lake, Manitoba. Briefly, REFERENCES the observations on these amblygonites, made R. & DAvrs, N. F. by dern6 et aJ. (1972), are: Bunrrmervr,C. W., Hor-rowlY, J. thJamblygonites (1969): properties of water to of the wall zone contain Thermodynamic 30 mole Vo F, increas- 1000'C and 10,000bars. Geol, Soc,Amer. Spec. ing to 30 to 50/o in zone 4 and to 4O to 55Vo Pap.132, in zone 5, but decreasing in the upper parts of (l972rz that zone. 7-rlnng of crystals in each pegmatite Crnlcl, I., CnnN?,P. & FERGusoN,R. B. pegmatite Bernic Lake, Manitoba. zone is toward The Tanco at lower F contents. Secondary IlL Amblygonite-montebrasites. Can. Mineral. montebrasite veins many of the earlier-formed rr. 643-659. crystals. ,_&_(1973):The The increases of F contents from zone 2 to 4 fluorine content and some physical properties of to 5 probably result from mechanisms 2 and the amblygonite-montebrasite minerals. Amer- 3 above. An increase of 25 mole % of F will Mineral. 58,291-30I. correspond to a temperature decreaseof about CoNNoLLy, J. P. & O'Hene, C. C. (1929): The 50oC in an open system. The slight decreasein mineral wealth of the Black Hills. Soat& Dakota F in each zone of the pegmatite seenN to sug- School Mines Bull, L6, 245-246. gest that each zone formed within a small tem- GALLAGHER,M. J. (1967): Phosphates and other perature interval, and amblygonite crystalliza- minerals in pegmatites of Rhodesia atd Uganda. tion caused a decreasein the IIF content of the Mtneral. Mag. 86, 50-59. SYNTHESIS OF THE AI\4BLYGONTTB SERIES 363

GINZBURG,A. I. (1950): Montebrasite ancl tle pro- tions of synthetic lepidolite. Amer, Mineral. 56, cess of its alteration. Trans. Mineral Museum 2469-2087. Acad. Sci. USSR 2, 72-85 (in Russ.). & Eucsrnn, II. P. (1969): Experimental HrrNnrcn, E. W. & Conev, A. S. (1955): Monte- control of fluorine relations in hydrothermal sys- brasite from Eight Mile Park, Fremont County, tems. Amer. Mineral. 54, 943-959. Colorado. Amer. Mineral, 40, II4L-1L45, QuENsEL, P. (1956): The paragenesis of the Varu- Houcnx, O. A. & WArsoN, K. M. (1946): Chemical trask pegmatite ingluding a review of its mineral Processes Principles Charts. John Wiley & Sons, assembledge.Arki,v Mineral. Geol. 2, 9't25, New York. Srwr,, D. R. & Pnorner, H. (1970): JANAF Ther- Lon, S. E. (1975): Synthesis and Fluorine-Hydroryl mochemical Tables.2nd ed. N,SRDS-NA^! .37. Exchange i,n the Amblygonite Sertes. M.A. thesis, Vr-esov, K. A., ed, (1966): Geochemistry and Min' Univ. California, Santa Barbara. eralogy of Rare Elements and Genetic Types of Moonr, P. B. (1973): Pegmatite phosphates. Miz- Their Deposits. Vol. 2 Mineralogy of Rare Ele' eral. Record 4, 103-130. ments, TralLsL from Russ. by Z. I*rman Daniel Moss, A. A., FuEn, E. E. & EMBREv,P. G. (1969): Davey & Co., N. Y. On the X-ray identification of amblygonite and montebrasite. Mi,neral. Mag, 37, 414-422. Manuscript received September 1975, ernended MuNoz, J. L. (1971): Hydrothermal stability rela- April 1976.