THE AMERICAN MINERALOGIST, VOL. 53, NOVEMBER DECEMBER, 1968

BEUSITE, A NEW MINERAL FROM ARGENTINA, AND THE GRAFTONITE-BEUSITE SERIES1

C. S. Hunr.nur, JR., exo L. F. AnrsrenerN, Departmentof Geolo gi c al Sci en c e s, H araar d, U nh ersity, Combrid ge, M ass achu s etts 0 2 1 3 I

ABSTRACT

Beusite, (Mn, Fe, Ca, Mg)3(POa),is the manganeseanalogue of graftonite and with it forms a continuous series. The new mineral was found in granite pegmatites in three localities in San Luis Province, Argentina: Los Aleros, Amanda and San Salvador. The mineral from Los Aleros has the following properties: It occurs in rough prismatic crystals up to 30 cm long, interlaminated with lithiophilite. Beusite is monoclinic, 2f m; space grotpP21/c,a:8.78,b:11.52andc:6.15 A,B:99"25',aibic:0.7621i1:0.5338;volume 613.7 N; Z:4. Strongest lines in X-ray powder photographarein A:3.50 (100), 2.863 (100), 2. 708 (60), 3. 13 (40), r.e24(40), 3.0 1 (3s), 2.Se (30), 2.4o2 (30). The new mineral is optically biaxial, positive,a:l702, p:1.703, t:1.722,2V:25", r)z strong, X:b ZAc:37o. The color is reddish-brown,cleavage: {010} good, {100} fair. The hardness is 5; density 3.702 (meas), 3.715 (calc). A wet chemical analysis recalculated to 100 percent is: CaO, 4 78; MgO, 2.64; FeO, 14.62; MnO, 36.56: PzOs, 41.40. DTA shows one endothermic peak at 960'C resulting from fusion. Optical properties, specific gravity and analyses by X-ray fluorescence and atomic absorption show beusite from San Salvador and Amanda to be similar to that from Los Aleros. The difierencesin the properties that result from changesin FeO:MnO ratio are offset by MgO and CaO making a chemical analysis necessary to distinguish between graftonite and beusite. The interlaminated lithiophilite is interpreted as exsolved from a high temperature disordered phase A wet chemical analysis of this mineral from Los Aleros recalculated to 100 percent is: LLO, 9.58; NarO, 0.03; FeO, 13.04; MnO, 23.02; Mgp,6.45; PzOr, 47.88. Optical properties of triphylite-lithiophilite from five localities and of graftonite from Ranquel and Cacique Canchuleta, all from San Luis, are presented. Beusite is named in honor of Professor Alexey Beus, formerly Professor of Mineralogy and Geochemistry, Moscow Polytechnical Institute.

fnrnooucrroN During a field study of granite pegmatites in Argentina (1964 and 1965) specimensof what appeared to be graftonite triphylite inter- growths were collectedfrom four localitiesin the Province of San Luis (Fig. 1). The most remarkablespecimens, because of sizeand freshness, came from the small pegmatitelocally known as Los Aleros.The others camefrom the mines: San Salvador,Amanda, and CaciqueCanchuleta. An additional specimenshowing a similar intergrowth from the Ranquel mine in the sameprovince was given to us by Dr. Maria A. R. Benyacar. The physical propertiesand X-ray powder photographsof the "graf-

l Mineralogical Contribution No. 457, Harvard University

1799 1800 C. S. HURLBUT, JR. AND L F. ARISTARAIN

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Frc. 1.Beusite and graftonite localities, San Luis, Argentina. tonite" pointed to the presenceof this mineral in all specimens.Ilowever, chemical analyses of the graftonite-like mineral from the first three aforementionedlocalities showed MnO to be in excessof FeO rather than the reversewhich is characteristicof graftonite. This indicated the necessitl, of discriminating between graftonite and the manganese analogue. A review of the literature shows uncertainty regarding the names applied to the minerals whose general formula can be expressedas (Fe, Mn, Ca, Mg)3(POr)r. De Tesris(1933) describedas mangualdite a mineral whose chemical anall'sis ,vieldeda formula close to 2MnO' CaO'PzOi, but whose ph-vsicalproperties were somewhat different from those of graftonite. Mason (1941) mentions the "graftonite- mangualdite group" (p. 119) thus suggestinga seriesexisted between the two minerals.Ilowever, in an addendum to the samepaper (p. 175) he found by X-ra.v examination of t1'pe material that mangualditeis a member of the apatite group. In 1950 Beus determined the weight percentagesof oxides in a graftonite-likemineral as: FeO, 16.95:MnO, 30.77;CaO, 0.54; XIgO, 9.50. The principal lines in a X-ray powder photograph of this mineral check with those of graftonite, but the physical properties are incom- plete. Beus stressedthe high content of MgO by naming the mineral magniophilite, although his was the first analysis of a graftonite-like mineral in which MnO was greater than FeO. Brooks and Shipwav (1960) also presenteda chemicalanall''sis (p. 522) of a "member of the graftonite isomorphottsseries" in which MnO exceedsFeO. Sincethe mineral of Brooks and Shipwal-(Australia) and the minerals BL.USITT. 1801 from Los Aleros, San Salvador and Amanda (Argentina) are ver,vlow in MgO (1.2 to 2.56 wt. /o) the name magniophilite is inapplicableto them. Recent chemical analysessuggest (see Fig. 5) that a complete solid solution exists, as in many other phosphates,between iron and manganesebut only partial solid solution with regard to magnesium and calcium. To avoid further confusionin the nomenclature,we pro- pose the name beusite for those members of the seriesin which the weight percent of MnO is greater than FeO. Beusiter (pronouncedbay' oosite)is named in honor of Alexey Beus, the first to report a mineral in the graftonite seriesin which Mn ex- ceeded Fe. Dr. Beus, formerly Professor of Mineralogy and Geo- chemistry, Moscow Polytechnical Institute, is at present a Technical Adviser to the United Nations Secretariat.

GBor,ocrcer SBrrnqc The beusiteand graftonite localitiesin San Luis Province,Argentina are located on the easternslope of the Sierrade San Luis. Thesemoun- tains, part of the SierrasPampeanas, begin at the city of San Luis and extend to the Sierra de los Comechingones,approximately 150 kilo- meters to the northeast. They are fault-block mountains with sharp escarpmentsto the northwest but tilted toward the southeastand rise abovesea level to an elevationof 2000meters, or 1500meters above the surroundingplains. The basementcomplex of the Sierrade San Luis is formed essentially of schists,gneisses, and quartzites, that have been intruded by granite with the formation of migmatites. The metamorphic rocks strike N-S with, in general,an easterly dip ranging from 40o to 90o. Genetically associatedwith the granite are abundant pegmatites and aplites. The ageof the basementrocks is given as pre-Cambrian(GonzLlez Bonorino, 1950;Linares, 1959)but other authors considerit Lower to Middle (?) Paleozoic.(Pastore and Ruiz Huidobro, 1952; Pastore and Gonz6les, 1954).The erosionfollowing the uplift of the sierra during the Tertiary removed most of the pre-Tertiary and Tertiary sedimentary rocks Ieaving only minor patches of Permian rocks. Finally, rninor effusions of Tertiary andesiticrocks and Quarternary basalts complete the gen- eral geologicpicture of the sierra. For details of the geologyof the region one is referred to the papers by Pastore and Ruiz Huidobro (1952). Pastore and Gonz6lez(1954), Gonz|lez (1957) and Methol.2

I'fhe mineral and name have been approved by the Commission on New Minerals and Mineral Names, IMA. 2 Methol, E. (1964) Descripci6n geol6gica de la Hoja 22 h, Santa Rosa, Provincia de San Luis, Argent Reprh Dir. Nac. Mineria. Unpublished. 1802 C. S. IIURLBUT, JR. AND L F. ARISTARAIN

OccunnBNcB The pegmatites of the Sierra de San Luis are tabular or lenticular, concordant bodies, generally zoned and manl' contain lithium and beryllium minerals.(Angelelli and Rinaldi, 1963;Herrera, 1963).All of them at which beusiteor graftonite werefound have commercialamounts of spodumene,beryl or muscovite, a characteristicof two-thirds of the reported graftonite Iocalities. The obscureLos Aleros pegmatite located in the Departamento de Pringles, San Luis Province, is 800 meters to the west of the large pegmatiteand beryl mine known as SantaAna. This mine can be reached by following a secondaryroad 35 kilometersfrom La Toma toward Paso del Rey and from this point following the mine road for 8 kilometersto the north. The Los Aleros pegmatite is tabular with N.S. strike and 80" dip to the east conformingto the enclosingmica schist.At the southernend of a small prospectpit (14 m long, 1.5 m wide,5 m deep) rough prismatic crystalsof beusiteup to 30 centimetersin length were collected.Triplite and tourmaline were found in addition to qtartz, microcline,plagioclase and muscovite. In the northern part of the Sierra de San Luis, approximately 100 kilometers from Los Aleros in the Departamento Junin, there are two beryl mines known as Amanda and San Salvador. On the dumps at both of thesepeglnatites, specimens of beusite were collected.Amanda is approximately 36 kilometers northwest of Santa Rosa south of the road between this town and Balde de Escudero. San Salvador is ap- proximately 20 kilometers NNW of Santa Rosa, west of the road from Santa Rosa to Punta del Agua. A few kilometerssouth of Los Aleros and south of the Pasodel Rey- La Toma road are the pegmatitesof Ranquel and Cacique Canchuleta operating for ber,'-land muscovite. Graftonite was collectedfrom the dump at Cacique Canchuletabut that from Ranquel was given to us. AII the beusiteand graftonite from theseArgentine localitiesare fresh with the exception of graftonite from Cacique Canchuleta which has partially altered to heterosite.This changeis similar to the first sl2oe nf alterationreported by Stanek(1955). Pnvsrcar ANDOPTrcAr, PnopnnrrBs Beusite. Fresh beusite from Los Aleros is reddish-brown with the cleavages:{010} good and {100} fair. Its hardnessis 5 and specific gravity, measuredon the Berman Balance is 3.702+0.005. The luster is vitreous and the streak pale pink. The optical propertiesare given in column 12 of Table 1. The physical propertiesof beusitefrom Amanda BEUSITI], 1803

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and San Salvador are similar to those from Los Aleros; their optical propertiesare summarizedin the sametable, columns 10 and 11 respec- tively. To compare the optical properties and specificgravities of the min- erals of the graftonite-beusiteseries, selected sets of values are given in Table 1 with FeO, MnO, CaO and MgO expressedas weight percent- age of the total amount of the divalent metal oxides. Included with these are data on graftonite from two new localities in Argentina, Ranquel and Cacique Canchuleta, columns 7 and 8 respectively.AII members of the seriesare optically positive and have strong to very strong dispersion with r)u. No pieochroism was observed in the mineralsfrom Argentina. No clearcut relationscould be establishedbetween optical properties, specificgravity and variation in chemical composition.However, as is to be expectedin an iron-manganeseseries, there is a trend for both indices of refraction and specifi.cgravity to increasewith increasing percentageof iron. At the sametime the effectof calciumand magnesium is to markedly decreasethese values offsetting the differencesrelated to iron and manganese.Consequentl)', optical and physical propertiesare not diagnosticin distinguishingeven thosemembers.of the serieshaving greatly different Fe: Mn ratios. For example,compare columns 4 and 12 of Table 1. Although, there are insufficientdata to generalize,a small axial angle may result from a high manganesecontent.

Intergrown mineral. Lithiophilite was identified as the mineral inter- laminatedwith beusitefound in all the SanLuis localities.The identifica- tion of this mineral from Los Aleros was made by chemicalanalysis and physical properties.The lithium mineral from the other localities was determined by optical properties and/or its alteration products. How- ever, for certain identification of triphylite-lithiophilite, the determina- tion should be verifi.edby chemicalmeans since the triphylite-lithiophi- lite seriesis subject to the same variation in properties as is this graf- tonite-beusiteseries. The optical propertiesand alteration products of the lithiophilite are summarizedin Table 2. Lithiophilite from Los Aleros is unusuallv fresh, with gray color, cleavage:{100} perfect, [010] fair, and {011} poor. The measured specificgravity is 3.365.The strongestlines in an X-ray'powder photo- graphare in A: 3.013(100), 2.525 (62),4.287 (62), 3.488 (48), 5.149 (32), 2.778(22),3.921 (22) and 2.463(20). Becauseof their high qualitl'the specimensfrom this locality offered an excellentopportunitv to studl'the rellrtionshipof the interlaminated mineral. Individual lavers of uniform thicknessextend for more than 10 BI'USITI' 1805

T,tnm 2 Oprrcal Pnopnnru:s eNn Ar-tBtarroN Pnolucrs ol TRtprtvr-rre- LrrnropgrlrrE" INrnRr-aMtNA.roo wrrn Bnusrrn eNl Gn.tltotrtn lnou SeN Lurs. AncrntrNa I 2v Sion Dispersion Alteration 80' r <1) fresh 250 + r1l partially to sicklerite 1.675 70" + r purpurite or heterosite 1.676 1.678 )J- r <1) partially to ferrisicklerite and heterosite

* Na light+0.001. centimeters(see Fig. 2) with their thicknessesroughly inverselypropor- tional to their density distribution. Observations made on three mutually perpendicular thin sections from a largefragment indicate that all the beusitelayers have a common crystallographicorientation. The lithiophilite on the other hand presents several optical orientations, as seen in Figure 3. The interface of the layers is an undulating surfaceessentially parallel to the best cleavage, 10101,of beusite.

, : t''':'.'.try :,',1',;t . ]

Iirc. 2. Fragment of beusitelithiophilite from Los Aleros, San Luis. The narrower bands are lithiophilite, darkened by a slight surface alteration' 1806 C. S, IIURLBUT, JR. AND L. F. AITISTARAIN

Ftc. 3. Beusite-lithiophilite thin section from the center of a cryslal Note the lithio- philite (dark) shows two orientations whereas the beusite is constant throughout. Crossed polars.

To establish the cr1'stallographicrelationship of the two minerals, fragments were selectcdcomposed of both phasesin which the orienta- tion of beusite was known. Using the optical goniometerthe cleavages of lithiophilite were identified and three types of intergrowth were established.Given in order of decreasingfrequency theseare:

Beusite Lithio. Beusite Lithio. (010)ll (110) and t1011ll tr10l (010)ll (s22) and t102)li tOT1l (010)ll (121) and t1001ll I2r0l Toward the edgesof the rough crystalsthe regular banding giveswav to a fine granular intergrowth of the same phases(see Fig.4). AII the characteristicsof the intergrowth argue more strongly for exsolution from a parent phase than does rhythmic deposition as suggestedby Penfield (1900) or replacementalong graftonite cleavagesby late stage pegmatitic solutions.The granular texture is interpretedas rapid cooling from crystal boundarieswith reducedionic mobility. The mineral intergrown with graftonite at Ranquel was established as triphylite by an electron microprobe analysis (Mn:Fe). That from Cacique Canchulelais completelv altered to purpurite or heterosite.

X-nav Sruov oF BEUSrrrt Beusite is monoclinic, 2f m. The extinctions in single crvstal X-ray precessionphotographs (Mo/Zr) taken with b and c as the precession axesyield the space group P2yfc the same as reported for graftonite by BELISITE 1807

Frc. 4. Photomicrograph of thin section of the granular intergrowth of beusitelithiophilite from the edge of a crystal. Crossed polars. Diameter of field 2 mm'

Lindberg (1950). Table 3 presentsthe cell dimensionsof beusite from Los Aleros,San Luis and of graftonitefrom the Nickel Plate Mine, South Dakota. The spacingsof beusite given in Table 4 were derived from powder

T,llr,n 3. UNrr-Crr,r, D.a.r.a.lon Bousrrn e.xo Gn,q.ltoNrrr

Graftonite" Beusite (Nickel Plate Mine, (Los Luis) Aleros San South Dakota)

& s.7sl 8.871 b 11.s21+o.otA 11s7f A c 6 1sl 6.17) p 99"25',+ 15', 99" 12',+15', atb:c O.7 621:1 :0. 5338 0. 766:1:0 .533 Cell volume A3 613.7 62s Z 4 4 Space group P21/c P2y/c Density: measured 3.702+0.005 3.775 calculated for (Mn1 77Fen7s 3.715 CaozgMgo z) (POr),

"Lindberg (1950), 1808 C. S. I]URLBIIT, JR. AND L. F, A]IISTARAIN

Tesr,r 4. X-Rev Powonr Dara lon Brt'srrn aNo GRelroNrrr (Fe Ka: 1.93728i\, Fe Ka1:1 93597 A; Mn filter) Camera diameter 114.59mm

Graftoniteb Graftoniteb

Los Aleros, San Luis, Argentina Nickel Plate, Los Aleros, San Luis, Argentina Nickel Plate, SD,USA, SD,US.A

d(obs) d(calc)c 1 d(obs) d (obs ) d (calc)c hklc I d(obs) AA A AA A 20 429 4 293 111 It oto 2+z\ 3 607 121 \r oos | 970 100b 3 4S 3 510 130 11 932 3 +62 220 40 t.926b 11.e27 1231 336 11.e20 060l 40 3.13 3,130 131 317 5 I 891 412 308 ata 1131 5 lr 1 875 35 3.01 3 021 702 302 Jr.szo i11 | z.oss 131l 1.831 061\ 25 294 ! 4 2 956 1.832 .l 1 836 12.e34 o12J l1 832 7

s This study b Lindberg (1950) c Calculated on an IBN{ 7094 Computer photographs(Cu/Ni) but with intensitiesobtained from diffractometer charts. The calculated ri values and indices were determined with an IBM 7094Computer. A comparisonof thesewith spacingsof graftonite from the Nickel Plate Mine given in the sametabie, showsno clear cut relation with chemicalcomposition. The sameis true for all the published d values of membersof the series.

Cunurcar ANarysris Bewsite.Beusite and lithiophilite from Los Aleros were separatedfor chernicalanal)'sis. Because the bands are comparativelywide and easilr- BI'USITI], 1809

Teelo 5. Cnnurcal ANlr,vsrs ol Blustrr rrlon Los Amnos, Sen Lurs, AtcnnrrNe

wt% Atomic proportions recalculated 2 4 (P:2)

CaO +.64 +.78 Ca 0.0852 0.2920 Mso 2.56 2.64 Mg 0.0655 0.2246 IreO 142 14.62 Fe 0. 2035 0.6976 MnO 35.5 36.s6 Mn 0-5154 1.7668 PrOr 40.2 +l 40 P 0. 5834 2.0000 Lt:O o.l+ o 2 3l1l 8.0020 Na:O none Sio: t.J H,O (-110"C) 0.17 HrO (+110'C) 0.8

Total

1. Dr. Jun Ito, analyst, by wet methods. A spectrographic analysis showed traces of Al, Na, Zn, Ag, Cu and Bi. 2. Analysis recalculated to 100 percent disregarding LirO, SiO, and HzO. split along the interface, relatively pure samplescould be obtained by hand picking. Wet chemical analyseswere made by Dr. Jun Ito on samplesthat were estimatedto be at least 98 percent pure. The results are given for beusitein Table 5 and for lithiophilite in Table 7. In column 4 of Table 5 are given the atomic proportions of beusite disregarding Li2O, SiO2 and HzO. These values yield the empirical formula (Mn1 77Fe6.76Cao:rgMgo.:z)(POr)rot (Mn,Fe,Ca,\4g)r.nr(POD, which is very closeto the theoreticalformula Rrz+ (PO+)2. The graftonite-like minerals from Amanda, San Salvador, Ranquel and CaciqueCanchuleta, were alalyzed by Dr. D. L. Giles.CaO, MnO, FeO were determined by X-ray fluorescence,and MgO by atomic ab- sorption.The resultsgiven in Table 6 show that the first two are beusite (columns15 and 17) and the last two are graftonite (columns12 and 13) with high manganesecontent. fn Dana's System of Mineralogy Vol. 2, 1951,it is stated that, "A limited isomorphous series extends between Fe, Mn and Ca, - - -". Sincethat time new analyseshave becomeavailable. These, as well as older analysesare summarizedin Table 6 and graphically presentedin Figure 5, in percentagesof the total divalent metal oxides.They suggest that a completeseries extends between Fe and Mn with a partial substi- tution bi' Ca and Mg. Becausethe molecularweights of FeO and MnO are very close,the 50 weight percent boundary between graftonite and i810 C. S- IIURLBUT. ]]1. lND L F'. ARISTAITAIN

Terr,r 6. Cnrurca.r, ANALl.'sESnor rnr Gn,qltoxrro-BBusrrr Sri

Graftonite

Meteoritic Pegmatitic

.] 9 10

CaO none 129 t2 80 923 5 .s0 600 Mco none 0.53 1441: 040 070 010 FeO 60 29 60 04 33 10,9 28 84 30.65 31 80 30 i0 i\{nO 310 9?:!t5 6.5 17 66 15 96 t7 62 21 80 21 81 PzOr 39 71 36 86b 40 81 41 08 41 65 41 20 38 20 39 66 H:O 0 5.5 075 060 060 Rem. 260 1 t'1 033 130 089 Total 100 00 1.0012 99 83 99 25 100 18 s9 90 99 76

FeO:MnO 1:0 ] I :0 05 1:0 48 1:053 1:055 1:0.57 1:0 69 wt.7"

Gra{tonite Beusite

Pegmatitic Synthetic

ll l2 13 14 15 l6 19 20

CaO 450 67 7.9 411 122 054 464 tr'rgo 26r 259 none 243 950 256 FeO 32 33 248 23 1 27 i8 168 16 95 t+2 i\'InO 23 22 206 21 1 25 18 21 I 30 77 3.5 5 59 99 PrO; 38 94 45 29b 45 31b 40 0J B 77b 42 53 402 40 01 HrO 054 060 042 097 Rem 122 164 Total 99 63 100 00 100 00 99 82 100 00 100 71 100.001ee. s 99 7l 100 00

FeO:MnO 1:0 72 1:0 83 1:0,, 1:148 l:1.90 1:2.36l:2 5O Wt 7o i a Analysis by wet methods; except as indicated b By difierence 1 \,'alues calculated for Fer(POr)r Synthesized by Korinth and Royen, 1961 2 4 X4exicanmeteorites: 2 Bella Roca I; 3 Chupaderos;4, Bella Roca II E O Olsenanalyst, by microprobe in Olsen and Frediksson, 1966,recalculateC from values given as wt. /6 of l'e and tr{n 5 Brissago,Switzerland, J Jakob, analrst, in Parker et al, 1939 6 East Alstead, New Hampshire, U S A Jun Ito, anal st, in llurlbut, 196.5 7 and 10 7 Rice }Iine, New llampshire, U.S,A 10 Nickel Plate trIine, South Dakota, U S A l{ L Lindberg,anal;'st in Lindberg, 1950. 8 Grafton, Neu'Hampshire, U S A S, L Penfield,anahst, in Penfield,1900 9 Sdo Luiz do Paraitinga, 56o Paulo, Brazil B A Ferreira, analyst, in Franco and Porto, 1952 11 Olgiasca,Italy P Gallitelli, analyst,in Grill, 1955 DescribedasrepossiLe (:graftonite, Strunz, 1939) 12,13, 15 San Luis, Argentina 12 Ranquel [4ine 13 Cacique Canchuletanline 15 Amanda l\{ine 17 San Salvador l{ine D L Giles, analyst, CaO, lfnO, FeO by X-ray fluorescence,NIgO by atomic absorption This study 14. Greenwood,n{aine, U S A J J Fahey,anallst, in Glassand Fahey, 1937 16 Kyrk-Bulaka, Turkestan llountains, U S S R A A Beus,anal,rst, in Beus, 1950 18 Beryl King Mine, Queensland,Australia in Brooks and Shipu'ay, 1960 19 Los Aleros, pegmatite San Luis, Argentina Jun Ito, analyst, from Table 5, column I This study. 20 Values calculated for Mna(POr)r. Synthesizedby Dorv Chemical Co BEUSITE

o pegm?ltitic a meteoritic

" sYnthetic Frc. 5. Composition of minerals in the graftonite-beusite series, in weight percent of total divalent metal oxides. Note the limited fields in which both the pegmatitic and meteoritic members fall. beusiteis essentiallyequivalent to 50 mole percent of the same oxides A differential thermal analysisof beusitefrom Los Aleros showsonly one thermal reaction, an endothermicpeak at 960oCresulting from fu- sion. The product is a black amorphouspellet, slightly magnetic.Like graftonite, beusiteis solublein acids. It has already been mentioned that it is impossible to distinguish unequivocally between graftonite and beusite by physical and X-ray means. This is becauseferrous and manganous ions convey similar propertiesto the mineralsand becausesmall percentagesof calcium and magnesiumgreatly effect theseproperties. We, therefore,wish to stress that only through some quantitative determinationof iron and manga- neseis it possibleto distinguishbetween members of the series.For this reason,beusite may be as abundant as graftonite but has been over- Iooked in the past and misidentifiedby physical means as graftonite.

Lithiophilite. The chemical analysis of lithiophilite from Los Aleros is given in column 1 of Table 7. From the atomic proportionsin column 4 the following empirical formula results: Lio u;(MnoasFe6.27Mgo.rr) POa oi which is closeto Li(Mn,Fe,Mg)PO+. A DTA curve obtained using this mineral shows a sharp endothermic peak at 890"C which is attributed to fusion. P-q.nBurMruonar Lindberg (1950)was unable to rationalizethe axial ratios of graftonite obtained by X-ray methods with those obtained by Penfield from morphology. This indicated the possibility that Penfield was dealing with a pseudomorphof graftonite-triphylite after a high temperature mineral. With the hope of arriving at the composition of the parent mineral the relative percentagesof the two phasesat Los Aleros were t8t2 C. S. HURLBUT, JR. AND L. F. A]TISTARAIN

Teerr 7. Cnnurcal ANALysrs ol Lrrnropnrr,rrE FRoM Los Ar,rros, SeN Lurs, ArcrNtrNa

wt ok wt 7o Atomic proportions recalculated (P:1)

1

Liro 9.40 958 Li 0 6412 0.950s Na:O 003 0.03. Na 0.0010 0.0015" FeO t2.8 13.04 Fe 0.1815 0.2690 MnO 22.6 23.02 Mn 0.3245 0.4810 Mgo 6.33 645 Mg 0.1510 0.2238 PrOu 47.O 47.88 P 0.6746 1.0000 CaO none SiOz 0.78 2.6646 3.9498 AlzO: 0.50 HrO- 110'C 0.10 H,O+110'C 0.15 99.69

n The arnount of NazO is so small lhat it is omitted in the empirical formula. 1. Dr. Jun Ito, analyst, by wet methods. A spectrographic analysis showed traces of Cu, Bi, Ba, Sr, and Ag. 2 Analysis recalculated to 100 percent disregarding SiOz, AhO: and HzO. determinedfrom thin sections.In bolh lamellarand granularintergrowth the volume percentageswere: beusite 82, Iithiophilite 18. Using these volumes, the chemical analysesof Tables 5 and 7, and the measured specificgravities, we arrive at a composition of the original material that can be expressedas (Lio.soMnr.ozFeoozMgo.zzCao.:+) (POs.su)z or (Li,Mn,Fe,Mg,Ca)a This suggeststhat the parent phasewas a "(POn)r. disorderedhigh temperature Iithium graftonite rather than a different mineral. In the formation of the low-temperaturcphases all the lithium became concentratedin the lithiophilite whereasall the calcium went to beusite. At the same time there was a substantial migration of Mn2+ and Fe2+ from the spacenow occupiedby lithiophilite toward the beusiteportion, and of Mg'+ it.,.the opposite direction. In a study of the banded graftonite-sarcopsidefrom Alstead, New Hampshire, Hurlbut (1965) assumeda migration of Ca2+ and Mn2+ to graftonite and of Mg'+ and Fe2+toward sarcopside.He reported the parent phaseto be a graftonite-likemineral. It seemsreasonable to con- clude that when the parent pegmatitic material does not contain lithium the exsolvedmineral is sarcopside.But when lithium is present triphylite or lithiophilite is exsolved depending on the Fe:Mn ratio. BNUSITN 1813

In all graftonite intergrowths reported (Penfield, 1900; Parker et al, 1939; Glassand Fahey, 1937; Berman, 1927) the associatedmineral is triphylite. In the 5 intergrowthsfrom Argentina mentionedin this paper all have triphylite-lithiophilite. Chemical analyses show that triphylite is present with graftonite at Ranquel but that lithiophilite is associated with beusite at Los Aleros.

AcKNoWLEDGWNTS

The writers wish to express their appreciation to Dr. Hugo E. Moni of the Geological Survey of San Luis Province, Argentina who, as a member of the expedition gave valuable assistance in the field. Thanks are also due to Dr. H. L. Rossetto and Mr. R. Tejeiro for providing us with unpublished reports from the files of the Instituto Nacional de Geologia y Mineria of Argentine Republic. Support of the work in both field and laboratory by grants (GP 2314 and GA 874) from the National Science Foundation is gratefuily ac- knowledged.

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Manuscript recei,aeil,Apritr 19, 1968; accepted.Jor publi.cation, Atr'gust 1, 1968