American Mineralogist, Volume 74, pages 1368-1373, 1989

Chayesite,K(Mg,Fe2+)oFe3+[SirrOrol: A new rock-formingsilicate mineral of the group from the Moon Canyon (Utah) lamproite DlNrpr.r-nVnr-on Laboratoire de P6trologieMin6ralogique, Universit6 P. et M. Curie (UA 0736 du CNRS), 4, PlaceJussieu, F-75252 Paris Cedex 05, France Orar MnoBNn.l,cH Institut liir Mineralogie, Ruhr-Universitat, Postfach 102148, D-4630 Bochum l, West Germany CnnrsrrlNn WAGNER Laboratoire de PdtrologieMin6ralogique, Universit6 P. et M. Curie (UA 0736 du CNRS), 4, PlaceJussieu, F-75252 Paris Cedex 05, France WnnNrn Scnnpvnn Institut fiir Mineralogie, Ruhr-Universitat, Postfach 102148, D-4630 Bochum 1, West Germany

Ansrn-q,cr Microprobe analyses(mean of l0 grains)of chayesitegave SiO, :69.19, TiO, : 0.25, AlrO,:0.20, Fe'O,:4.88, FeO: 6.60,MnO :0.29, MgO : 12.71,Na'O:0.31, KrO :5.17, total: 99.60wto/o,leading to the formula (basedon O: 30, with Fe valences partitionedto give Si + Al + Fe2++ Fe3++ Mg + Mn + Ti : 17) (K, ,oNao,o)", ,o(Mg, ,nFefrjrMno.oo)*.oo(Fe3.toFet.lnAlo ooTio03)>1 ooSir2 ooO30 oo. The idealizedend-member is K(Mg,Fe'?+)oFe3*[Si,rOro],which (with Mg:Fe'z+'Fe3+: 3.32:0.99:0.69)requires SiOr 69.l5, FerOr 5.28,FeO 6.82,MgO 12.83,KrO 5.92,total 100.00wto/0. X-ray powder data prove chayesiteto be a member of the osumilite group. It is related to roedderite,(Na,K)r(Mg,Fe)r[Si,rOro], by the substitutionFe3+ + tr : Fe2++ (Na,K). The strongestpowder lines are 7.14 (st) 002, 5.08 (vst) I 10, 3.75 (vst) 202,3.24 (vst) l2l, 2.782 (st) 204. Chayesite is hexagonal,probably P6/mcc (by analogy with the osumilite group)wirh a : 10.153(4)A, c : 14.388(6)A, V : 1284.4L', Z: 2. Chayesiteoccurs microscopically as a late-crystallizing phase in a lamproite at Moon Canyon, Utah, U.S.A. The crystalsare deep blue, transparent,and tabular; their is white, and their luster is vitreous. They show no .D^":2.68 g/cm3.Uniaxial positivewith

INrnooucrroN AND occuRRENCE the common elementsNa, K, Mg, Fe2+,Fe3*, and Al mostly present in members of the osumilite group, the The osumilite-$oup minerals form a constantly grow- milarite-type minerals as a whole may also contain other ing family of double-ring silicates with a milarite-type elementsuch as Li, Be,B, Ba, Sn, andZr, aswell aswater. structure. Six-membered double rings are linked by R,+ The present publication deals with the description of octahedra and by distorted tetrahedra. A review of mi- chayesite,a new member of the osumilite-group that has larite-type minerals was publishedby Forbeset al. (1972), been found as a rock-forming mineral in a lamproite who gave their generalformula as from Utah and probably also in a lamproite from Canca- rix, Spain. It has the idealized formula K(Mg,Fe'z+)o- 2tcrel8216lArr4lT(2)3 rrElDrr [r41T(I )' rOro]. Fe3*[Si,rOro] and is related to roedderite, (Na,K)r- (Mg,Fe'?+)r[Si,rOro],by the substitutionFe3* + E : Fe2+ This crystal-chemical formula allows for the incorpo- + (Na,K). Thus it contains only one alkali atom per for- ration ofcations with very different sizesand leads to an mula unit like osumilite itself, which has a composition enormous chemical variability and complexity. Besides nearK(Mg,Fe'z+ )2A13 [A12Si]oo3ol. 0003-004x/89/l r l 2-1368$02.00 r368 VELDE ET AL.: CHAYESITE l 369

Within the osumilite group, a chemical distinction is made by Bunch and Fuchs (1969) betweenthe Al-rich Choyesite,Moon Conyon osumilite- subgroup and the Al-poor merrihueite- Choyesrte,Concorix roedderitesubgroup, the latter being definedby an atomic Roedderite,Eifel Mountoins ratio Si/Al > 7. Chayesite thus belongs to the merri- hueite-roedderitesubgroup. = Chayesitehas been found in lamproite specimenMC7, o- originallydescribed from Moon Canyon,east of Francis, Summit County,Utah, by Bestet al. (1968).It is present d in all thin sections cut from this specimen but has not o beenfound in other samplescollected from the sameout- tl. crop. Unlike roedderite, which in terrestrial occurrencesis restricted to melt-coated cavities in gneiss xenoliths in volcanic rocks (Hentschelet al., 1980),chayesite is part of the igneous mineral assemblageand apparently crys- tallized as a late phasefrom the lamproite liquid. A min- eralogicaldescription of the Moon Canyon lamproite al- (K*No) p.f.u. .j::L* ready mentioning the new phase was given by Wagner and Velde (1986,p. 27-28). Fig.1. Plotofcalculated Fe3+ contents ofchayesite (this study) andselected roedderite from theliterature versus alkali contents The name hasbeen given in honor or Dr. Felix Chayes, analyzed.For methodofcalculation, see text. Solid line indicates a petrologist formerly on the staffof the GeophysicalLab- the substitutionfrom ideal chayesiteto ideal roedderiteend- oratory of the Carnegie Institution of Washington and members.Dashed line separatesthe chayesiteand roedderite past-presidentof the Mineralogical Society of America. solidsolution fields as defined by the alkali values. Dr. Chayes showed deep interest in the mineralogy of alkaline rocks before creating a new discipline, statistical petrology. The name and mineral have beenapproved by ring silicate.If the method of calculatingthe Fe2+/Fe3+ the InternationalMineralogical Association. ratios as outlined above is used,however, the Si values Type material has been deposited in the collections of per formula unit of Table I show only a small scatter the Institut fiir Mineralogie, Ruhr-Universitdt, Bochum, around 12.00.For valuesbelow 12.00.some Al can be F.R.G., as well as in the Museum of Natural History used to complete the tetrahedral T(l) sites to the ideal (Smithsonian Institution), Washington, D.C., U.S.A., occupancy(analyses l-3 of Table l). Only analysis4 shows numberNMNH 165807. a somewhatlarger deviation from the theoretical Si max- imum of 12.00.The generallyexcellent fit of the tetra- Crrnlrrc,c.L coMposrrroN hedral and octahedral occupanciesis consideredindirect Table I gives selected electron-microprobe analyses support for the calculationsas well as for the presenceof covering the range of chemical composition of chayesite a considerableamount of Fe3+.The presenceof Fe3+is from the Moon Canyon sample,together with some anal- also in ag.reementwith the deep blue color of chayesite, ysesofterrestrial roedderite from the literature. Analyses becauseGoldman and Rossman(1978) have alreadyin- wereperformed with an automatedcAMEBAX electron mi- terpreted the very similar blue color of most osumilites croprobe at the Laboratoire de P6trologieMin6ralogique, as being due to Fe2+-Fe3+charge transfer. Paris. Experimental conditions were the following: accel- It can also be seen from the empirical chayesite for- eration voltage, l5 kV; current intensity, l0 nA; counting mulae of Table I that the excessof the alkali sums (K + time, 30 s; standardswere oxides or natural minerals. No Na) over 1.00-that is, over that of the idealizedchay- elementswith atomic number >9, other than thoselist- esite formula K(Mg,Fe'z*)oFe3+[Si,rOro] -is charge-bal- ed, were detected.An ion-microprobe analysis showed a anced by a numerically similar deficiencyof Fe3+against very small amount of Li, but not enoughto be considered 1.0. The data are plotted for a total of l0 chayesiteanal- a significant constituent of the mineral. The Fe3+/Fe2+ ysesin Figure I and provide good evidenceforthe cation ratios were calculatedby assumingfull occupancyfor all substitution Fe3+ + [ : Fe2+ * (Na,K), which relates tetrahedraland octahedralsites, bringing this cation sum the idealized chayesiteend-member given above to roed- without the alkaliesto ) : 17.0 and charge-balancingthe derite,(Na,K)r(Mg,Fe,*)r[Si,rOro]. Analysis A of Table I total cations including the alkalies against 30 . and Figure I representsa terrestrial exampleofroedderite It should be emphasized here that a recalculation of (Hentschelet al., 1980) recalculatedaccording to the the structural formulae of chayesitewith the assumption method used in the presentpaper. that all Fe is present as FeO leads to impossibly high Si The substitutionalmechanism Fe3+ + E : Fe2+* Na+, values per formula unit (up to 12.18) and to sums of which leaves a vacancy in one of the alkali sites, has tetrahedralplus octahedralcations far above 17.00,which alreadybeen suspected by Hentschelet al. (1980)as well cannot be accommodated in the structure of a double- as bv Abraham et al. (1983)in analvticalstudies ofblue t370 VELDE ET AL.: CHAYESITE

c o Choyesrte, Moon Conyon ", A Choyesite,Concqrix + O Roedderite,Eifel Mountoins o) ^\t + -a 02 Fig. 4. Idealized sketch of chayesite morphology (compare LL oc Fie. 3). o0 -o LL oA o2 04 UO No/(No*11) It is interesting to note in this connection that the sub- stitution Fe3+ * ! : Fe2+ + Na* linking chayesiteand Fig. 2. Fe,.,/(Fe.",+ Mg + Mn) versusNa/(Na + K) plot roedderite was also shown to occur in osumilite itself, showingnegative correlation for the chayesiteand roedderite for alkali deficienciesbelow 1.00 analysesofFig. 1. where it is responsible per formula unit (Schreyeret al., 1983). As the new mineral chayesitecontains Fe3+ as an es- sential component, minimum amounts of Fe are present roedderite crystals from the Eifel, Germany, in order to in the solid-solution seriesfrom roedderite to chayesite, explain their observed alkali deficiencies. The micro- increasingfrom zero for pure roedderite to one Fe3+per probe analysesof thesecrystals are also included in Table formula unit for the chayesiteend-member (seeFig. l). I and Figure l, as C and D, respectively, after recalcu- Figure 2 actually indicates that the degree of chayesite lation according to the above scheme. Figure I shows substitution is correlated with the total Fe content of the quite impressively that there may be a complete solid crystals. Table I shows that there is always an excessof solution between roedderite and chayesite. Thus roed- total Fe over the required amount, so that significant derites D and C have some 25 and 40 molo/oof chayesite amounts of Fe2+are present as well. Figure 2 also con- component,respectively, in solid solution,and the Moon firms that it is mainly Na-rather than K-that varies in Canyon chayesitecrystals are not of ideal end-member the roedderiteto chayesileseries. composition, but contain up to about 40o/oof the roed- Prrvsrcnr, PRoPERTIES derite end-member. The systematic deviations of the analysesplotted in Figure I from the ideal solid-solution In the Moon Canyon sample studied, chayesiteforms line can probably be explained by very small analytical very small (mostly less than 50 1tm, rarely up to more errors in the microprobe analyses,because-except for than 100 pm) euhedralto subhedralcrystals (Fig. 3). Even the alkalies-all the elementsdetermined, and even the in thin section,the mineral exhibits a decidedly blue col- presenceoftrace elementsnot analyzedso far, contribute or. The habit is tabular with the dominant faces{0001}, to errors in the calculated Fe3+values. { 1010},{1120}, and { l0I2}, which arealso common for other milarite-type minerals (Fig. 4). No twinning has been observed.The mineral is transparentwith a vitreous luster and a marked pleochroism with O : sky blue and ,E : colorless.The crystals are brittle with no apparent cleavage.Hardness and density could not be measured becauseof the small grain size. The calculated density is 2.68g1cm3. Chayesiteis uniaxial positive,with co: 1.575(l) and e : 1.578(1),measured in Na light (\: 589 nm) on iso- lated small grains. In thin sections,a slightly higher bi- refringencethan 0.003 was suspectedfor some chayesite - crystals. The compatibility index is excellent with I (Kp/K): -0.034 accordingto the classificationof Man- darino(1981). Optical properties do not difer significantly between the members of the osumilite-type minerals. For exam- ple, blue color and a positive optical sign are exhibited by many osumilites (Schreyeret al., 1983) and some Fig. 3. Tabular, euhedral chayesite crystal coexisting with roedderites(Abraham et al., 1983).Given thesesimilar- K-feldspar in the groundmass of Moon Canyon, Utah, lam- ities and the nearly identical X-ray pattern (seebelow), proite, sampleMC7. (a) Plane-polarizedlight.(b) CrossedNicols. only chemical analysescan lead to a proper identification. VELDE ET AL.: CHAYESITE t37l

TABLE1. Selectedresults of microprobeanalyses of chayesitecompared with analyses of roedderite

Chayesite Roedderite

sio, OY.Y5 69.86 69.47 69.35 69.68 70.60 71.10 71.10 Tio, 0.21 0.21 0.36 0.23 0.17 0.07 0.10 0.07 Al2o3 0.24 0.17 0.34 0.21 0.16 0.50 0.27 0.61 0.05 0.00 0.00 FerO3* 5.28 6.17 5.bz 3.30 4.51 2.55 0.68 0.21 FeO- 5.40 4.27 c.zt 9.32 7.68 3.50 3.84 0.78 MnO 0.23 0.21 0.23 0.35 0.39 0.21 0.26 0.37 Mgo 13.64 13.90 13.39 11.61 12.30 15.70 16.50 18.85 CuO 0.03 0.00 0.13 ZnO 0.15 0.00 0.34 Naro 0.45 0.25 0.29 0.43 0.33 1.80 2.24 3.32 K.O 5.24 5.14 5.18 5.28 5.31 4.20 4.28 4.33 2 100.64 100.19 100.13 100.08 100.53 99.11 99.20 100.09 Structuralformulae on the basisof 30 oxygens 5l 11.96 11.96 11.94 12.07 12.03 12.02 12.08 11.92 AI 0.04 0.03 0.06 0.00 0.00 0.00 0.00 0.08 1200 11 .99 12.00 12.07 12.03 12.02 't2.08 12.00 Ti 0.03 0.03 0.05 0.03 0.02 0.01 0.01 0.01 AI 0.01 0.00 0.01 0.04 0.03 0.10 0.05 0.04 Cr 0.01 0.00 0.00 Fe3* 0.68 0.80 073 0.43 0.59 0.33 0.09 0.03 Fe* 0.77 0.61 075 | .JO 1.11 0.50 0.55 0.11 Mn 0.03 003 0.03 0.05 0.06 0.03 0.04 0.05 Mg 3.48 J.C+ 3.43 3.02 3.16 3.98 4.18 4.70 Cu 0.00 0.00 0.02 Zn 0.02 0.00 0.04 s.00 5.01 5.00 4.93 4.97 4.98 4.92 5.00 K 1.14 1.12 1.14 1.17 1.17 0.91 0.93 0.93 Na u. tc 0.08 't 0.10 0.15 0.11 0.59 0.74 1.08 29 1.20 1.24 1.32 1.28 1.50 1.67 2.01 NoteiChayesite analyses from sample MC7, Moon Canyon, Utah. Roedderite analyses from Hentschelet al. (1980)(cols. A andC) andAbraham et ar.(1983) (cor. D). . Formethod of recalculation.see text.

Cnysr,ll,r-ocRApHy A sBcoNr occuRRENcE oF CHAYESTTE Single-crystalstudies could not be carried out because Although not confirmed by X-ray data, chayesitemost of the small size of the isolated crystals. Thus the unit- probably occurs also in a lamproite from Cancarix, Al- cell parameterswere refined from X-ray powder-diffrac- bacete,Spain, where it has already been mentioned as a tion data of several of these very small single crystals new phaseby Wagnerand Velde (1986,p. 27-28) as well. obtained with a Gandolfi camerawith CuKd (Ni-filtered) In this rock, the mineral has been detectedas a rare ac- radiation. The refined unit-cell parameters are a : cessoryphase of minute crystal size only in one thin sec- 10.153(4)A, c : 14.388(6)A, and V: 1284.4A, lTable tion, whereasother sections from the same sample and 2). The c/a ratio calculated from unit-cell parametersis from other specimensof this locality appear to be devoid 1.417t. of it. Suchsporadic occurrence is reminiscentof the Moon The crystalsare hexagonaland probably belongto space Canyon locality-where chayesitehas been found in only group P6/mcc (by analogy with the osumilite-type min- erals);Z: 2. The X-ray powder-diffraction pattern was indexed in Tlele 2. Latticeconstants and somephysical properties of analogyto that of osumilite (Table 3). The chayesitepat- chayesitefrom Moon Canyon and other minerals of theosumilite group tern shows three very strong reflections with d : 5.08, 3.75, and 3.24 A. Theseare also strongreflections in the pattern of the synthetic Mg-osumilite end-member a(A) | 0.078 10.138 10.14-10.1s 10.153(4) (Schreyerand Seifert,I 968)with d : 5.04,3.7 3, and 3.21 c(A) 14.317 14.302 14.22 14.388(6) A respectively. The X-ray patterns for other osumilite- D(g/cm3) 2.624 2.629 2.67 2.69 1.539 1.543 1.543 1.575(1) group minerals, i.e., merrihueite (Dodd et al, 1965), C 1.548 1.544 1.578(1) roedderite(Olsen, 1967),yagsife (Bunch and Fuchs, I 969), A/ote:(1)Osumilite,KMg,Al3(Si,oALOs),Schreyerand Seifurt, 1968(ASTM/ and even the new B-bearing member poudretteite (Grice 29-1016).(2) Roedderite,Hentschel et al., 1980.(3) Eifelite,Abraham et et al., 1987),have their strongestreflections at similar d al., 1983. (4)Chayesite, refined from 19 reflections(Gandolfi pattern, CuKq, values. cameradiameter: 114.6 mm). t372 VELDE ET AL.: CHAYESITE

TABLE3. X-ray powder-diffractiondata for syntheticosumilite This situation also afects the Fe3+calculation and results and for chayesitefrom Moon Canyon in too low a value. Thus, the Cancarix analysis plots in basis ofits Osumilite. Chayesite.' Figure I along the ordinate, although on the alkali content, it is actually closer to the ideal chayesite om ilh end-member,K(Mg,Fe2+)oFe3*[Si'rOro], than the Moon 8.72 a Canyon phases.In Figure 2, the Cancarix mineral also 718 7.14 7.194 st 002 15 5.56 5.568 102 plots along the ordinate near the Fe,o,/(Fe,o,+ Mg + Mn) s.04 60 508 5.076 vst 110 value of0.4, thus extendingthe trend from roedderiteto 4.36 14 4.38 4.396 200 chayesiteto a practically Na-free and most femrginous 4.12 40 4.14 4.148 m 112 3.73 45 375 3.751 vst 202 member. 3.s8 3.61 3.597 004 The above chemical featuresseem to confirm that the 2n 331 3.35 3.329 m 104 phaserepresents chayesite as well, probably the 3.21 100 3.24 3.238 vst 121 Cancarix 2.995 11 3.01 3.017 122 purest one yet found. However, owing to its extreme rar- 2.919 60 2.933 2.9350 m 114 ity and the minute crystal size, the necessarysupporting 2.768 65 2.782 2.7840 st 204 2712 12 2.736 2.7316 213 data have not been obtained thus far. 2 518 14 2.542 2.s382 m 220 2 412 11 2.388 Qh 2.398 2.3981 006 2.377 Prrnor,ocrc DIScussIoN 2 159 12 2.176 2.1754 w 215 The mineral most closely related to chayesite, i.e., 2 088 4 2.103 2.1022 w 402 where it 2.071 2.0739 vw 224 roedderite, was first reported from meteorites, 2.OO4 1( 2.019 2.0185 w 314 occurs either with enstatite, , and (Fuchs 1.904 2 et al., 1966) or with forsterite, F-richterite, albite, and 1.888 10 1.903 1.9018 w 411 1 850 20 1.859 1.8604 w 315 krinovite (Olsen, 1967; Olsen and Fuchs, 1968).In ter- 1 793 14 1.799 1.7992 w 008 restrial rocks, roedderite and the more sodic mineral ei- 1.755 2 feliteoccur in melt-coatedcavities within gneissxenoliths 1 746 t) 'l 1.734 18 742 1.7431 m 226 ejectedby tephritic lavas of the Eifel province (Hentschel 1.689 4 1.695 1.6953 w 118 et al., 1980;Abraham et al., 1983).They are interpreted 1.570 1.5701/1.5698 w 4231511 1.439 1.4390/1.4388 w 425100.10 as precipitates from alkaline, Mg- and Si-rich, but Al- . deficient gasphases. Unlike thesetwo minerals, chayesite FromSchreyer and Seifert(1968) (ASTM/29-1016). groundmass ". Gandolfipattern, CuKa, camera diameter 114.6 mm. occurs in the igneous and must have crys- t Abbreviationsare vst : very strong, st : strong, m = medium, w : tallized from the lamproite melts. It is associatedwith : weak,vw very weak, b: broad. the late-crystallizing phasesK-feldspar, minute crystals of , and an unidentified Ti-rich phase, but is slightly later than K-richterite. There is no petrographic observation that could indicate that richterite had be- one rock sample thus far-and may be indicative of a come unstable. The only phasesunstable at this stageof nonuniform distribution of chayesitein lamproites as a the solidification were olivine and Ti-rich phlogopite. whole. Nonuniform distribution would certainly account Forbes (1971) and Charles (1975) have shown that for the fact that chayesitewas overlooked in two well- roedderite,associated with forsterite, diopside, melt, and studied localities for such a long time. vapor, is a low-pressurebreakdown product ofrichterite A representativemicroprobe analysis of the Cancarix (between930 'C and 970 "C at 50 bars and 150 bars, mineral yielded the following results:SiO, 70.29; TiO, respectively).Fe-bearing roedderite is also a decomposi- 0.02;Al,O, 0.00;FeO (: Fe.,) 12.60;MnO 0.23;MgO tion product of the sodic amphibole riebeckite, forming 11.44;NarO 0.04; KrO 4.48. Thus this mineral has a at pressuresbelow 500 bars (Ernst, 1968).Since in the considerablyhigher Fe/Mg ratio than the chayesitefrom two lamproites from Moon Canyon and Cancarix, the Moon Canyon. potassicassemblage chayesite + K-richterite is found in- Employing the recalculation method for Fe3+ intro- stead of roedderite and Na-richterite, we may consider duced earlier, the structural formula of the Cancarix min- that chayesite belongs to a low-pressure assemblage eral becomes formed from melt with a composition closeto K-richter- ite. (K nrNaoo,)",oo(Mgr ruFeljMno orFefljr)"o rrISir, 18O30]. Chayesitehas so far not been synthesized,and thus no This is certainly close to the chayesiteformula, if com- direct experimental information is available on its ther- pared with the formulas of Table l. However, there is a mal stability. However, attempts to estimate the temper- disturbing excessof Si over 12.00that is most unlikely ature of crystallization of lamproites have been made in for a double-ring silicate. The deficiency against 5.00 in many casesand give temperaturesbelow 965 "C for the the remaining tetrahedral and octahedral sites may indi- latest phasesto crystallize (Wagner and Velde, 1986). cate the presenceof additional elements although none The presenceof chayesitein the two lamproites testifies were detected,but the sample was not analyzedfor Li. for the strongpotassic peralkaline character ofthese rocks VELDEET AL.:CHAYESITE t373 as well as for progressiveFe enrichment with the crys- mineral from the Indarch meteorite. American Mineralogrst, 51,949- tallization of theseMg-rich lavas. 955. Goldman,D.S., and Rossman,G R. (1978)The sitedistnbution of AcxNowr,rncMENTS and anomalousbiaxiality in osumilite American Mineralogist,63,490- 498. We are greatly indebtedto M. G. Best,Brigham Young University, Salt Grice,J.D, Ercit, T.S.,van Velthuizen,J., and Dunn, P.J.(1987) Poud- Lake City, Utah, who generouslydonated fragments of his MC7 specimen retteite, KNarB,Si,rOro, a new member of the osumilite group from from the Moon Canyon locality, thus making this study possible.A useful Mount Saint-Hilaire, Quebec,and its .Canadian Min- review ofthe manuscript by E. J. Olsen is gratefully acknowledged. eralogist,25, 763-7 66. Hentschel, G., Abraham, K., and Schreyer,W. (1980) First terrestrial occurrenceofroedderite in volcanic ejectaofthe Eifel, Germany. Con- Rr,rnnnNcnscrmo tributionsto Mineralogyand Petrology,73,127-130. Mandarino,J.A. (1981)The Gladstone-Dalerelationship: Part IV. The Abraham, K, Gebert, W., Medenbach,O., Schreyer,W., and Hentschel, compatibility concept and its application. Canadian Mineralogist, 19, (1983) G Eifelite,KNa,MgSi,rO,o, a new mineral of the osumilite 441450. group with octahedral . Contributions to Mineralogy and Pe- Olsen, E. (1967) A new occurrenceof roedderite and its bearing on osu- trology, 82, 252-258. milite+ype minerals. American Mineralogist, 52, | 5 19-1523. Best, M.G., Henage,L.F., and Adams, JA.S. (1968) Mica peridotite, Olsen,E, and Fuchs,L. (1968)Krinovite, NaMgrCrSirO,o:A new me- wyomingite, potassic and associated igneousrocks in northeastemUtah. teoritemineral. Science, 161, 786-787. AmericanMineralogist, 53, l04l-1048. Schreyer,W., and Seifert, F. (1968) Metastability of an osumilite end- Bunch,T.E., and Fuchs,L.H. (1969)Yagiite, a new sodium- member in the system &O-MgO-AlrO.-SiOr-HrO and its possible analogueof osumilite.American Mineralogist, 54, l4-18. bearingon the rarity ofnatural osumilites Contributions to Mineralogy Charles,R.W. (1975) phase The equilibria ofrichtente and ferrorichterite. and Petrology, 14, 343-358. -3'1 American Mineralogist, 60, 367 4 Schreyer,W., Hentschel,G., and Abraham, K. (1983)Osumilith in der van Dodd, RT., Jr., Schmus,W.R., and Marvin, U.B. (1965) Merri- Eifel und die Verwendung diesesMinerals als petrogenetischerIndi- hueite, a new alkali-ferromagnesiansilicate from the Mezij-Madaras kator. TschermaksMineralogische und PetrographischeMitteilungen, chondrite.Scrence. 149. 972-9'l 4. 31,2rs-234. Ernst,W.G (1968) p Amphiboles,125 Spnnger-Verlag,New York. Wagner, C, and Velde, D (1986) The mineralogy of K-bearing lam- (1971) Forbes, W.C. Synthesis and stability relations of richterite, proites.American Mineralogist, 7 1, l7 -37. NarCaMgrSiOrr(OH)r. American Mineralogist, 56, 997-1004. Forbes,W.C., Baur, W.H., and Khan, A.A. (1972)Crystal chemistry of milarite-type minerals. American Mineralogist, 57, 46347 2. Mexuscnrpr REcETvEDFssnuanv 13, 1989 Fuchs,L.H, Frondel, C., and Klein, C., Jr. (1966) Roedderite,a new MANUSCRTPTACcEPTED Jurv 17, 1989