Lamellar Structure of Rhodonite and Pyroxmangite Intergrowths

Home , Jacobsite, Pyroxferroite, Pyroxmangite, Rhodochrosite, Rhodonite, Spessartine

American Mineralogist, Volume 69, pages 270-276, l9B4

Lamellar structure of rhodonite and pyroxmangiteintergrowths

Nonuyuxr Alxewl

Department of Geosciences, Faculty of Science Osaka City University, Sugimoto, 558 Osaka, Japan

Abstract

Reflectionsfrom X-ray and electrondiffraction patterns of intergrowthsof rhodoniteand pyroxmangiteare diffuseparallel to c*. Relativelysharp reflections correspond to ordered rhodonite or pyroxmangite. High resolution lattice fringe images show that units of rhodoniteand pyroxmangiteare intergrownas thin lamellaeless than 300Athick with (001) in common. Broadeningof the powder X-ray lines and variation in the observedoptical angle,2V, are explainedon the basisof the lamellarstructure of the two minerals.

Introduction complex covering Paleozoic sediments, occurs with The paragenesis and intergrowth of rhodonite and quartz, rhodochrosite,pyrite, sphaleriteand other metal pyroxmangite have been discussedby Burrell (1942), sulfides(Suzaki, 1963).The filling temperaturesof fluid (1963, yoshimura Momoi 1968),Suzaki (1963), (t967), inclusionsin quartzassociated with rhodoniterange from Trommsdorff et al. (1970)and Ito (1972.).Maresch and 160to 200'C. The "rhodonire" from the OhedaniMine, Kyoto Prefectureand from the Kiyokawa Mine, Tokyo are both in strata-boundmanganese ore depositsembed- ded in Paleozoicsediments. The Ohedani "rhodonite" occurswith quartz,rhodochrosite, tephroite and spessartine. The deposit has been regionally metamorphosed, and belongsto the epidote-actinolitezone of the green- shistfacies (Hashimoto and Saito, 1970).The Kiyokawa "rhodonite" occurs as veinletscutting rocks containing ent. (1979) Aikawa reported that intergrown rhodonite rhodochrosite,hausmannite, jacobsite, tephroite, bemen- and pyroxmangite have a constant orientation relation; tite and spessartine.A petrologic study has not been a16 ond brhare nearly parallel to ao, and bor, respectively, carriedout, but it is consideredthat the deposithas been crhmakes an angleof abour 4. with co, on 1110),and the regionallymetamorphosed, perhaps under zeolite-facies chemical compositions of the two minerals are different conditions. A preliminarysurvey of thesespecimens using powder X-ray diffraction methods resulted in their identification as a mixture of the two mineralsas describedby Momoi (1963)and Suzaki (1963).Fragments of rhe specimens were then studiedby single-crystalX-ray methods.The cell dimensionswere measuredfrom a-, b- and c-axis or more unit cells thick in the c-axisdirection. precessionphotographs, and the profilesofdiffuse reffec- (1963) Momoi and Suzaki(1963) described two charac_ tions were measuredusing a densitometer.The chemical teristics of rhodonite-pyroxmangiteintergrowths: (l) compositionsof the fragments(remounted and polished broadening of reflections of the powder X-ray parrern, after the single crystal X-ray experiments) were deter- and (2) anomalousvalues of the optic angle2V. In order mined using a JXA-SA electron probe microanalyserwith to understandthese characteristics,this study of inter- PET and RAP wavelength-dispersive crystal spectro- growths of rhodonite and pyroxmangite from various meters.An acceleratingpotential of 15 kV and a sample localities has been carried out. current of 0.01 pA on MgO were the operatingcondi- tions.The beamcurrent was digitized Specimens and experiments with countingtimes of 10 seconds on each of 5-10 areas of each grain Three samples ..rhodonite" usedin this study are from analysed.Synthetic MgO, SiO2, Al2O3, CaSiO3,MnO, different localities. The fibrous rhodonite from the Sankei Fe2O3and natural albite (Amelia, Virginia) were used as Mine, Hokkaido, which is a Au-Ag-Cu-pb-Zn hydro_ standardsfor all analysis.Analyses were carried out in thermal vein type deposit embedded in a green tuf the standard fashion with focused beam. Data sets were 0003-004)vE4l03M-0270$02.00 270 AIKAWA : RHODON ITE-PYROXMANGITE INTERGROWTH'S 271 reduced following the method of Bence and Albee (1968) sponding to various phases, including: rh(s)' rh(s) + using the o-factors given by Nakamura and Kushiro py(d), rh(d) + py(d), rh(d) + py(s) and pv(s), where (s) (1970).An electronmicroscope (Hitachi HU-l2SE) oper- and (d) denote sharp and diffuse reflections, respectively. ating at 100kV and equippedwith an energy dispersiveX- However, the specimensfrom Sankeigive only two types ray analyzer was used for transmission electron micros- of diffraction patterns; rh(s) + py(d) and rh(d) + py(s)' copy. The specimenfrom Kiyokawa was preparedby ion and no single-phasecrystal or sampleofrh(s) + py(s) has milling a specimen from a thin section which was first been detected. The specimensfrom Ohedani always give oriented using single-crystalX-ray methods. sharp reflections of types rh(s), rh(s) + py(s) and py(s). The electron diffraction patterns are similar to X-ray The difrraction pattern diffraction patterns. In Figure 2 are shown strong and Severalprecession patterns are shown in Figure 1. The sharp reflections colTespondingto rhodonite and pyrox- shapeof the diffuse reflections is columnar parallel to c*. mangite connected by streaks parallel to c*. However, The profile of the diffuse reflections obtained using a intensity maxima which cannot be indexed with rhodonite densitometer parallel to c* is symmetrical around the or pyroxmangite cell parameters, are relatively sharp, intensity maxima. The positions of the intensity maxima and are superimposed on diffuse streaks, were often correspond to those from ordered rhodonite or pyrox- observed in electron diffraction patterns. The intervals mangite. The orientational relation of the two minerals is between intensity maxima along diffuse streaks are not in good agreement with that described previously constant even in the same diffraction photograph, and (Aikawa, 1979). also are different among diffraction photographs from Crystals from Kiyokawa give diffraction patterns corre- different areas of the same crystal.

Fig. l. Precessionphotographs of rhodonite and pyroxmangite intergrowths. (A) and (B). The 0/t/ net of the specimen, rh(d) + py(s), from Sankei. Two sets of reflections are apparent. One set of reflections is marked by the axes b+o" and c*o", and is due to pyroxmangite;the other set ofreflections, marked by the axes b*.6 and c*,6, is due to rhodonite. The reflectionsfrom pyroxmangite are sharp, and those from rhodonite are diffuse. Photograph(A) was taken with MoKa radiation, 120hr. exposure' Photograph(B) was taken with FeKa radiation, 150hr. exposure.(C) and (D). The 0/c/net of the specimen,rh(s) + py(d), from Kiyokawa. Two sets ofreflections are apparentas in Figures 1A and lB. The sharp reflectionsare due to rhodonite, and the difuse reflections are due to pyroxmangite.Photograph (C) was taken with MoKc radiation, 100hr. exposure.Photograph (D) was taken with FeKa radiation, 120 hr. exposure. 272 AI KAWA : RH ODON ITE-PYROXMANGITE I NTERGROWTHS

mens. This result reconfirms the relation that rhodonite is more Ca-rich than pyroxmangite when the two minerals coexist(e.g., Aikawa, 1979;Winter et al., 1981;Brown et al., (1980). Pyroxmangite from the Kiyokawa Mine has less than 3 moleVoCaSiO3, and rhodonite has more than about 8 mole%oCaSiO3 (Aikawa, 1979).Thecomposition- al ranges of intergrowths of these two phases from the Kiyokawa Mine is thus between 3 and 8 moleVoCaSiO3. Twenty grains of the Sankei "rhodonite" were selected for analysis, but were not examined by single-crystalX- ray methods. The results are shown in Table 2. The Sankeispecimens contain a larger amount of CaSiO3.The composition of the Sankei "rhodonite" is divided into two ranges; one contains about 6-9 moleVoCaSiO3, the other about 13-17moleVo CaSiO3. This is shown to relate to two types of difraction patterns, rh(d) + py(s) and rh(s) + py(d), respectively. Pyroxmangite from the San- kei Mine has less than about 6 moleVo CaSiO3 and rhodonite has more than about l7 moleVoCaSiO3. Winter et al. (19E1)reported compositionsof rhodonite-pyroxmangite pairs from Bald Knob, North Carolina, together with previously published data. The results of this study, especiallythose ofSankei "rhodonite", do not agreewith those reported by Winter et al. (1981).The difference in the composition ranges of the two intergrowth minerals from diferent localities may reflect different geological environmentsofformation of the specimens(Peters et al., 1977;Peacor et al., 1978;Brown et al., 1980;Winter et al., 1981).

Electron microscopy of rhodonite and pyroxmangite intergrowths Rhodonite and pyroxmangite intergrowths show faults, planar and parallel to (001) as shown in Figure 3a, which Fig. 2. Electron diffraction patterns and X-ray difraction are the same as those Ried and Korekawa (1980) ob- pattern of rhodonite and pyroxmangite intergrowths from served pyroxenoids. Kiyokawa. (A) shows sharp reflections of rhodonite and in natural and synthetic There is no pyroxmangite connected by strong streaks, in which intensity strain at these faults. and the contrast on both sides of a maxima are observable. (B) and (C) show 20/ reflections of the fault is quite uniform (Fig. 3a). The separationbetween electron diffraction photographs of two diferent areas of a these faults is about 50 to 300A. Due to the faults. the crystal. (B) does not show well-defined subsidiary reflections, diffraction patterns show streaks parallel to c* as shown but (C) shows relatively sharp subsidiary reflections. (D) shows in Figure 2. In order to elucidate the nature of the faults, 20/reflections of the precessionphotograph of the crystal usedin high resolution lattice fringe images were obtained. The electron microscopy. complex lattice fringe images(Fig. 3b) are similar to those of synthetic pyroxenoids as reported by Ried and Kor- ekawa. Thesefringes are also parallel to (001)and there is Chemical composition no strain at the boundary. The widths of all fringes The specimensconsisting of two-phaseintergrowths or coincide with d661of rhodonite and pyroxmangite, where of a single phase which were previously identified by d661is nearly equal to c . sina : 0.9c (Ried and Kor- single crystal X-ray methods have been examined using ekawa,1980). There are homogeneousareas consisting of an electron probe microanalyser. The specimens were about 5-20 repeats offringes of rhodonite or pyroxman- scannedparallel and perpendicular to the c axis in order gite and heterogeneousareas consisting of intergrowths to detect any chemical inhomogeneity, but none was of l-3 fringes correspondingto rhodonite and pyroxman- found at the l-2 pm resolution limit of the probe. The gite. However, fringes with widths corresponding to resultsare listed in Table l. pyroxenoidswith periodicities greater than 9 silicon tetra- The Ca content decreasesin the order rh(s) + py(d), hedra were not observed. The complex and fine scale rh(d) + py(d) and rh(d) + py(s) in the Kiyokawa speci- lamellar structure describedin this study are explainedby AIKAWA: RHODONITE-PYROXMANGITE INTERGROWTHS 273

Table l. Analysesofrhodonites and pyroxmangites

Loca I i ty Kiyokawa Mine Sankei Mine Sample K-I K-2 K-3* K-4 K-5 pv py (s) +rh (d) py (d) +rh (d) py (d) +rh (s) rh** py (d) +rh (s)

sio2 47.40 46.B8 45.9O,47.75 48.43 47.45 4't.34 A1zo3 o. 05 0.07 0.08, 0.06 0.06 0.03 0.59 MSO 0.96 r. 50 0.94, 1.04 0.70 0.78 0.87 FeO*** 0.42 0.45 0.43, O.49 0.35 1.03 0.31 Iuno 5L 37 50.69 50.09, 50.74 50.53 45.60 44.r8 CaO L.37 1.37 2.Ol-, L.94 2.-17 6.36 7.11 Total 101.58 r00. 97 99.45,1O2.02 1or.3r tor.24 100.41 cations relative to 30 oxygens 10.04 9.98 9.96, 10.04 9.98 10.00 9.98 A1 0.01 0.02 o-o2, 0.02 0.02 0.01 0.15 Mg 0.30 o.4B 0.30, 0.33 0.22 0.24 o .27 FE 0.08 0.08 0.08, 0.09 0.06 0.18 0.31 Mn 9.2L 9.L4 9.2r, 9.04 9.t0 8.14 8.06 0.31 0.31 0.47, 0.44 0.63 I.44

*Data of different points in same grain. **This occurs at boundary of bedded manganese ore body and massive chert. ***All assmed to be Fe2+. (s)= sharp' (d)= diffuse.

"chain periodicity faults" which were first found in Discussion naturaland syntheticpyroxenoids by Ried and Korekawa (1980);it can be completelyexplained by the occurrence The repeatdistances of subsidiaryreflections in elec- of pyroxmangite(rhodonite) repeat units within rhodonite tron diffraction patterns are not regular, differ from those (pyroxmangite). reported by Ried and Korekawa, and do not show the

Table 2. Analysesof rhodoniteand pyroxmangiteintergrowths from the SankeiMine

sample t 3 e 7 910 sIo" 45.41 46,34 45.54 46.15 46.04 45.74 45.01 4b.65 C0. JZ 0.02 0.03 o.24 0.04 0.04 0.05 o,29 0. 04 ' Ms6 L,O7 r. 12 r-r5 f.uo ]. 19 0.88 0.92 FeOr 0.28 o.25 0,26 o.2a MnO 49.66 49,14 49,97 49.85 49.58 49,61 49.37 49.08 49,04 44.64 CaO 2,8r 2.86 2.99 3,r1 3.29 l. )r Na^O 0.03 0.0s 0.06 0.03 0.00 0.00 o.o2 0. 00 0. 00 0.03 ToEa 1 99.95 100.74 r00.03 100.99 100.24 100.06 I00.78 IOO.22 Cations relatiue to 30 oxygens ql 9,94 9.92 9.84 o o< o ol 9. 88 o oa o AI 0.0r 0. 05 0.01 0. 06 0.01 0.01 0. 0l 0.0? 0.01 0.05 M9 0.35 0.36 0.34 0.38 0.28 0.33 0.30 !-e 0.05 0.04 0.05 0.05 0.05 0.05 0. 05 0,05 0.05 0.65 a.67 o.61 0.70 0.73 o,16 0.81 0.81 0.87 NA 0,01 0.02 0.03 0.01 0. 00 0.00 0.01 0.00 0.00 0.0I

SanpI e r1 )-2 14 15 16 1-7 18 19 20 45.3r 45,88 46.13 56,01 46.32 45.15 46.01 45.55 A1r01 o.29 0.30 0.37 a.64 0.52 0. 15 0.15 0,22 - Mso 0.90 0.78 o.19 0.82 0. 84 0.81 0.88 0.86 0.s0 FeO* 0.30 0.35 0.30 0.28 o.29 0.30 0.3r 0.29 MnO 46.36 46,'70 46.44 46,09 45.44 44.40 44.65 44.9A 44.00 CaO 5.82 6.73 6.96 7.51 M"o 0. 02 0. 03 0. 00 0. 04 0.02 0. 00 o.o2 0,03 0.00 0.00 To€a1 100.34 99.85 99.99 100.13 9't.92 91.95 99,2A 99,37 Cations relative to 30 oxygens s1 9.90 9.90 9, 89 9.84 9.88 9.96 AI 0,07 0,0? 0.08 0. 09 0. r3 0.04 U.U5 0.04 0.06 Mg 0.29 0.3r 0.25 o.26 o.26 o,2a !e 0.05 0.06 0.05 0. 05 0. 05 0.05 0.05 0.06 0.05 Mn 4.42 a.44 8. 48 8,43 8.28 8.20 8.26 8.20 I 6l Ca t.27 t.29 r. 30 1.34 1.4r r.4s NA 0.01 0.0r 0. 00 o. 02 0.01 0.00 0.01 0.0r 0. 00 0. 00

*AI1 asgMed to be Fe 274 AIKAWA: RHODONITE-PYROXMANGITE INTERGROWTHS

Fig' 3. Bright-field micrographsusing 00/ reflectionsof rhodonite and pyroxmangiteintergrowths from Kiyokawa. (A) shows many faultswith separationsof 50 to 3004. (B) Lattice fringeimages. Widths of fringescorrespond to dsolof rhodoniteor pyroxmangite.

features such as doublets or triplets near reflections of observed in X-ray diffraction patterns, and only the rhodonite or pyroxmangite. Moreover, the diffraction relatively sharp reflections corresponding to rhodonite patterns of different portions of a crystal are different and pyroxmangite connected with strong diffuse streaks from eachother, as describedpreviously. This showsthat could be observed,as can be seenin Figures I and 2d. the areas giving diffraction patterns have diferent and The line broadening of the powder diffraction pattern irregular arrangementsof chain periodicity faults. On the (Fig. a) can be explained by the same relations. other hand, subsidiary reflections could not be observed There is no strain at the faults. However, cell dimen- in X-ray diffraction patterns. The X-ray diffraction pat- sions of rhodonite and pyroxmangite intergrowths as tern represents the average of the different electron shown in Table 3 are somewhat different from those of diffraction patterns from various areas of a crystal, be- single phase rhodonite or pyroxmangite; that is, b is causethe volume of crystal (about0.5 x 0.3 x 0.2 mm in longer and c is shorter than those of single phase rhodo- this study) contributing to X-ray diffraction is very large nite or pyroxmangite. This may be explained as simply compared with that (about I x I x 0.1 p.m) for electron being due to strain caused by coherency of the lamellar diffraction. Therefore, subsidiary reflections could not be boundaries. AI KAW A : RH ODO N ITE_P YROXMA N GITE I NTERGROWTH S 275

anglescompared with those of single-phaserhodonite and pyroxmangite. The intermediate values of 2V are thus explained by the lamellar structure. The thickness of lamellaeis small in comparisonwith the wavelengthused for the measurementof 2V. lf diferent domains of the crystal have different ratios of rhodonite and pyroxmangite as can be seen in Figure 3, then they must have different values of the average 2V. The ang)e 2V may therefore vary over different portions of a crystal. Accordingto Ried and Korekawa (1980),their synthetic Fe-rhodoniteand pyroxferroite have the samechemical composition. As described previously, Winter et al. (1981)and Aikawa (1979)showed that rhodonite is Ca- rich and pyroxmangite is Ca-poor when the two minerals coexist in nature. The present results of chemical compositions of rhodonite and pyroxmangite intergrowths using EIMA are in good agreement with those of coexisting natural pyroxenoids, although each of the two minerals could not be separately analyzed. In order to clarify the difference in chemical compositions of the two minerals existing in such fine-scale intergrowths, an analytical electron microscope was used, but it failed to elucidate the difference.This must be related to the resolution limit of the method,which is about 5004. Why did the complex natural rhodonite and pyroxmangite intergrowths form? Synthetic Fe-rhodonite and pyroxferroite intergrowths might be formed during crystal growth and natural rhodonite and pyroxmangite intergrowths might also be formed by the same process. However, it may also be necessary to consider some post-crystallizationprocess such as exsolution. Pyroxen- oids in nature always contain Ca, Fe, Mg, etc. substituted 30 32 34 36 38 40 for Mn, so the experimental results obtained by Maresch 2, dagr.G.(Fc Kr) and Mottana (1976) cannot be directly applied, and it is difficult to predict the change of P-T conditions of the Fig. 4. PowderX-ray diffraction patterns between l4o and l8o transformation between multicomponent rhodonite and and between30o and 2()" in 2O(FeKc)of pyroxmangite(A), mixturesof rhodoniteand pyroxmangite from differentlocalities pyroxmangite. However, it is very interesting that rhodo- (B, C andD) anda singlephase rhodonite (E). A: Ohedani.B: nite and pyroxmangite intergrowths in nature consist of Sankei.C: Kiyokawa.D: Ohedani.E: Nodatamagawa,Iwate separateparallel blocks of rhodonite and pyroxmangite Prefecture. and thus differ from synthetic Fe-pyroxenoids. More- over, the conditions offormation ofrhodonite and pyroxmangiteintergrowths used in this study are quite different from those of the syntheticFe-pyroxenoids; that is, the Becausemost of the chemical and physical properties specimensin nature are considered to be formed under pyroxmangite of rhodonite and are very similar, it is low temperature(200-400"C) and low pressure(less than difficult to distinguish between them by ordinary chemi- approximately 3 kbar) conditions. Therefore, the natural physical cal and methods. However, the optic angle,2V, rhodonite and pyroxmangite intergrowths may be formed pyrox- is very different; that of rhodonite is 63-87" and by a process different from that of synthetic Fe-pyrox- (Deer (1963)pointed mangite 37-4e et al., 1978).Suzaki enoids. out that specimensgiving broad reflections in powder X- ray patterns show a wide variation in 2V ranging from 40 Acknowledgments to 72". The values of the specimen from the Kiyokawa The writer wishesto expresshis thanksto Prof. Y. Ohashi, Mine obtained using a universal stage have been con- Universityof Pennsylvania,and Dr. K. Koto, OsakaUniversity firmed to fall in the range of 48-70" (4E,52, 52,64 and 70), for criticalreading of the manuscriptand manyhelpful sugges- although the number of measurementsis only five. Ho- tions.Dr. K. Nobugai,Osaka University, assisted with transmis- mogeneously strained rhodonite and pyroxmangite as sion electronmicroscopy. I shouldlike to thank Prof. D. R. describedin the last paragraphmust give diferent optical Peacorand Dr. E. J. Essenefor improvingthe manuscriptand 276 AIKAWA : RHODONITE_PYROXMANGITE INTERGROWTHS

Table 3. Chemical compositionsand cell dimensions

Locality sample Composition Cell dinension (cations) .til b(i) crit c(.) B(") y(") '1 K-l py(s) CarMgrt'tnnare, 6.70 .60 I7 .42 113.8 82.3 94.8 6.70 ?.63 82.4 t-r- PY(s) ca3Mg5Mn91Fel 17.35 113.8 94.8 d rh(d) - not determined - - ! rd o -. ^ Dv(d) ct5Mg3Mt9LF"t 6.72 7.67 L7.39 113.8 82.4 95.4 6 .: ii' iai 6.70 7.62 L2-L9 r11.0 84.9 94.4 >E "-' i? x-+ PI ldl carMgrl,tnrrre, 6.75 7.70 17.38 It3.6 rn(s, 6.7L 7.64 12.20 111.3 85.r 94.4 K-5 rh(s) cal4Mgruntrre, 6.73 7.68 t2.25 111,5 85.0 94.4 '6' --rh(d)q-r PY(s) not detemined 6,75 7.65 I7.37 114.1 82.6 94.3 o 6.72 7-65 12.15 110.6 85.2 93.5 J4tr.d pv(cr.l I E ^ ^ Cal5MgrMnrOFe, 6.74 7.7L 17.35 113.I 82.7 94.8 I "-" iit(s) 6.72 7.67 L2.23 111.3 85.2 94.2

Ehe interaxiaJ- angles are accurate to about 5 minutes, and the cell edges to approximately 0.2 to 0.3t rdith corrections made for fitm shrinkase,

for helpful advice. A part of the cost of this work was defrayed Mineralogical Society of Japan, 8, Special Issue 2, 1-6 (in by a researchgrant from the JapaneseMinistry of Education. Japanese). Nakamura, Y. and Kushiro, L (1970)Compositional relations of References coexisting orthopyroxene, pigeonite and augite in a tholeiitic andesitefrom Hakone Volcano. Contributions to Mineralogy Aikawa, N. (1979)Oriented intergrowth of rhodonite and pyrox- and Petrology, 26, 265J7 5. mangite and their tradSlormation mechanism. Mineralogical Peacor,D. R., Essene,E. J., Brown, P. E. and Winter, G. A. Journal. 9. 255-269. (1978)The crystal chemistry and petrogenesisof a magnesian Bence, A. E. and Albee, A. L. (1968) Empirical correction rhodonite. American Mineralogist, 63, 1137-1142. factors for the electron microanalysis of silicate and oxide. Peters,Tj., Trommsdorff, V. and Sommerrauer,J. (1978)Man- Journal of Petrology, 76,382403. ganesepyroxenoids and carbonates:Critical phaserelations in Brown, P. E., Essene,E. J. and Peacor,D. R. (1980)Phase metamorphic assemblegesfrom the Alps. Contributions to relations inferred from field data for Mn pyroxnes and pyrox- Mineralogy and Petrology, 66, 383-388. noids. Contributions to Mineralogy and Petrology, 74, 417- Ried. H. and Korekawa. M. (1980)Transmission electron miner- 425. alogy of synthetic and natural Fiinferketten and Siebenerket- Burrell, H. C. (1942)A statisticaland laboratory investigationof ten pyroxenoids.Physics and Chemistryof Minerals,5, 351- ore types at Broken Hill, Australia. Harvard University Ph.D. 365. Thesis(not seen;extracted from Deer et al., l97E). Suzaki, Y. (1963)Pyroxmangite, rhodonite and bustamite series Deer, W. A., Howie, R. A. and Zussman, J. (197E)Rock- minerals. GeoscienceMagazine, 14,72-87 (in Japanesewith Forming Minerals. Vol. 24, John Wiley and Sons Inc., New English abstract). York. Trommsdorff, V., Schwander,H. and Peters,Tj. (1970)Mangan- Hashimoto, M. and Saito, Y. (1970)Metamorphism of Paleozoic osilicate der alpinen Metamorphosein Radiolariten des Julier- greenstonesof Tamba plateau, Kyoto Prefecture. Journal of Bernina-Gebietes.Schweizersche Mineralogische und Petro- the Geological Society ofJapan, 76, l-6. logischeMitteilungen, 50, 539-554. Ito, J. (1972)Rhodonite-pyroxmangite peritectic along the join Winter, G. A., Essene,E. J. and Peacor,D. R. (1981)Carbon- MnSiO3-MgSiQ in air. American Mineralogist, 57, 865-876. ates and pyroxenoids from the manganesedeposit near Bald Maresch, W. V. and Mottana, A. (1976) The pyroxmangite- Knob, North Carolina. American Mineralogist, 66, 278-289. rhodonite transformationfor the MnSiO3composition. Contri- Yoshimura,T . (1967)Supplement to "Manganeseore depositsof butions to Mineralogy and Petrology, 55,69-:79. Japan". Science Reports, Department of Geology, Kyushu Momoi, H. (1963)Some problems on pyroxmangite. Journal of University, 9 (Special Issue), 245-270(in Japanese). the Mining and Metallurgical Institute of Japan, 79, 836-837 (in Japanese). Manuscript received,June 30, I98l; Momoi, H. (1968)Some manganesepyroxenoids. Journal of the acceptedforpublication, August 30, 1983.