ENGINEERING RESEARCH INSTITUTE UNIVERSITY OF MICHIGAN ANN ARBOR QUARTERLY REPORT NATURAL MICA STUDIES (Covering period September 1, 1952, to November 30, 1952) By E WM.,HEINRICH Associate Professor of Mineralogy Project M978 SIGNAL CORPS, U, So ARMY DA-36-039 sc-15357, SC PROJECT NO. 1~52B-0O, DA PROJECT NO. 3-99-15-022 December, 1952

- ENGINEERING RESEARCH INSTITUTE * UNIVERSITY OF MICHIGAN QUARTERLY REPORT NATURAL MICA STUDIES (Covering period September 1, 1952, to November 30, 1952) GENERAL During tho past three months several phases of work on the natural micas have been completed and the following papers have been accepted for publication in the American Mineralogist: 1. Studies in the mica group; Mineralogy of the rose muscovites, by E. Wm. Heinrich and Alfred A. Levinson. 2. Studies in the mica group; Relationship between polymorphism and composition in the muscovite-lepidolite series, by Alfred A. Levinson. Work has continued or is nearing completion on several projects discussed in the last quarterly report. These include structures of the high-silica muscovites (phengites) and of the biotites. Progress on the phengites was held up temporarily, as several critical specimens described in the literature were being sought from foreign investigators. Most of these have now been received, and it is planned to have the manuscript on structures of the phengites completed shortly. Temporary difficulties also have been encountered in the study of the biotites. During the past quarter the x-ray machine did not operate for about three weeks because of difficulty in obtaining a specific microswitch. Furthermore, it has been found impossible to distinguish the various polymorphs of biotite and phlogopite by the powder method. The photographs contain only a few of the strongest reflections (whose spacings appear to be identical for the various forms) with a very dark background. The possibility that this difficulty may be overcome by use c-; monochromator is being investigated. Nevertheless, single-crystal work on the biotites has continued. It is hoped that this phase of the study will be completed by the middle of January.

ENGINEERING RESEARCH INSTITUTE * UNIVERSITY OF MICHIGAN Two large projects have been started during this quarterly period. Mr. D. W. Levandowski has undertaken a study of the zinnwaldites, and Mr. C. H. Hewitt is studying zoning and overgrowths in micas. It is hoped that a complete paragenetic chemical and structural study of zinnwaldite will enable a definite decision to be made as to its relationship to other members of the mica group. With respect to the zoning and overgrowth study, since there are differences of opinion in the literature on the subject and since an excellent collection of specimens illustrating these relationships is available at the Minerological Laboratory,a detailed investigation seems desirable. Such a study should yield valuable information on progressive chemical and structural changes in the micas during the crystallization. lifetimes of their deposits. Both phases will probably be finished in time for the next quarterly report. Through the courtesy of Dr. Robert Hatch, seven samples of lepidolites and muscovites are now being analyzed at the Electrotechnical Laboratory of the U. S. Bureau of Mines, Norris, Tennessee. These samples were carefully separated during the past quarter from specimens from the Brown Derby pegmatite, Gunnison County, Colorado. The paragenetic relationships and structure of these micas are well known. The problem involved is to determine the relationship between chemical variations, paragenetic position and polymorphism in micas from a single pegmatite. Similar studies are planned for other pegmatites that contain micas of several generations. In the past two or three years several investigators have been attempting to explain polymorphism -in such minerals as micas and SiC by means of the screw dislocation theory. A brief study of this approach has been inaugurated with the translation from French of an unpublished Belgain paper, obtained through the courtesy of Professor Ralph Grim of the University of Illinois. Tentative plans have been formulated for the final report on this project. A detailed outline has been drafted, and it is expected that work on various sections of the final report may be initiated toward the end of the next quarter. SYSTEMATIZATION OF THE NATURAL MICAS Introduction A workable systematization of the micas has long been one of the aims of the project. Recently a preliminary classification based on structural and chemical data, along with an account of the very voluminous synonomy of the micas, has been completed. In the following pages this

- ENGINEERING RESEARCH INSTITUTE ~ UNIVERSITY OF MICHIGAN classification is presented. It is however, subject to revision for the final report. The numerous attempts at mica classification in the past have been based almost entirely on their chemistry and fall generally into two categories: (1) those employing complex quasistructural formulae (e.g., Clark, 1889; Jacob, 1925); and (2) those involving calculation of theoretical endmember molecules (e.g., Tschermak, 1878; Kunitz, 1924; Stevens, 1946). Berman (1937) approached the problem in more realistic fashion by correlating mica formulae with unit cell contents and expressed the chemical variation by means of atomic ratios of different elements occupying equivalent structural positions. However, the work of Hendricks and Jefferson (1939) Levinson (1953), and others has demonstrated the complex polymorphism in the mica group and the necessity for both chemical and x-ray studies of micas as a basis for a sound classification. Because of the complex chemistry of the group, the numerous textural and other minor varieties, and repeated misapplication of names, the nomenclature and synonomy of the micas have been ponderous and involved. The purpose of this work is threefold: (1) to present a reasonable and usable subdivision of the micas into naturally occurring species and major varieties on the basis of both chemistry and structure; (2) to review the synonomy of the group and thus assign minor varietal names or duplications to the species or major variety to which they correspond; and (3) to list those micas that are of indeterminate status owing to incomplete studies. In the annotated classification that follows we have used for chemical varieties the prefixes of Schaller (1930). Wherever possible for each entry we list. (1) a simplified formula based on 24 negative ions in the unit cell; (2) the major isomorphous substitutions; (3) the structure; (4) notes; and (5) synonymy. For the structural varieties, the method of polymorphic notation suggested by Ramsdell (1947) is adopted. The symbols and their meanings used in this work are as follows: 1M 1-layer monoclinic structure 2M muscovite 2-layer monoclinic muscovite structure 2M 2-layer monoclinic octophyllite mica structure 3M 3-layer monoclinic structure 3R 3-layer rhombohedral structure 6M 6-layer monoclinic structure 6T 6-layer triclinic structure 24T 24-layer triclinic structure 48T 48-layer triclinic structure 5

ENGINEERING RESEARCH INSTITUTE * UNIVERSITY OF MICHIGAN Chemical-Structural Classification of the Micas Species lo Muscovite, K2A14(Si6A12g802 (OH)4. Minor Na, Rb, Cs, Ba, and Ca for K; minor Mg, Fe, Mn and Li; Minor Fe3, Ti, and Cr for Al; minor F for OH; maximum Li 0 = 3.50, occupying vacant octahedral positions. Structure: 2M. muscovite. Synonyms: adamsite, ammochrysos, amphilogite, biaxial mica, cat gold, cat silver, common mica, damourite (in part), didrimite, didymite, ferro-ferri-muscovite, frauenglas, helvetan, heptaphyllite, isinglass, kaliglimmer, marienglass, monrepite, nacrite, oblique mica, potash mica, schernikite, zweiaxger glimmer. Hypothetical end-members: ferri-muscovite, kryptotile, leverrierite, lithium muscovite. Varieties. a. Barian muscovite. Ba with reported maximum of 5.91%BaO (Doelter, 1914) for K. Structure: probably 2M muscovite, material labeled oellacherite from Tyrol has the 2M muscovite structure. The barium-muscovite from Franklin Furnace, New Jersey, described by Bauer and Bertnan (1933), was examined by us by means of the x-ray powder method. The resultant pattern is not that of a muscovite, nor even that of a mica. the material is too fine-grained for detailed optical Studies. Synonyms: barium muscovite, oellacherite, sandbergerite. b. Manganian-muscovite. Reported maximum MnO = 2.32% (Ellsworth, 1932); usually some Li20 present. Structure: 2M muscovite. The very fine-grained, deep purple mangan-muscovite of Eskola (1914) with 2.35 MnO has been checked by us by means of x-ray powder photographs, and the pattern does not correspond to any known mica structure. The photograph shows some quartz lines; thus a chemical analysis of purified material is necessary. Synonyms: mangan-muscovite, manganese muscovite. Ferrian muscovite. Fe+3 with maximum of 5.70% Fe205 (Tschermak, 1878) reported, for Al. Structure: probably 2M ________________________________ 4 ________________________________

- ENGINEERING RESEARCH INSTITUTE * UNIVERSITY OF MICHIGAN muscovite, for the "alurgite" from Cajon Pass (Webb, 1939) with 5.32% Fe203 has been shown to have this structure. d. Ferroan muscovite. Fe+2, with maximum of 6.55% FeO (Wilfing, 1886) reported. Structure: probably 2M muscovite. e. Chromian muscovite. Reported maximum of 4.81% Cr203 (Whitmore, et al., 1946), for Al. Structure: 2M muscovite. This follows the usage of Whitmore et al. (1946). Synonyms: chromglimmer, chrome glimmer, fuchsite, gaebhardite, verdite. f. Lithian muscovite. K2(A14, Li) ca 5o0 (Si6-5, A12_3)8 020(0H3+F)4. Li2O, at least 3.30% occupying vacant octahedral positions. Usually small amounts of F for OH Structure: modified 2M muscovite (Levinson, 1953). g. Phengite. K2(Mg,Fe2)ASi7Al iAl)8020(oOH)4 High-silica muscovite with considerable MgO (7.96% Pagliani, 1937) and in some cases FeO; some Fe3 for Al. Structure' 2M muscovite. The nomenclature of the silica-rich end of the muscovite series as proposed by schaller (1950) is regarded by us as unsatisfactory because: (1) there is some evidence that the original leucophyllite (Starkl, 1883) is a mixture, and in any event a new analysis and an x-ray study of the type material are needed to check its validity; and (2) the term, alurgite, which Schaller (1950) suggests as a substitute for leucophyllite, in the event that the latter should prove untenable, also has been erroneously employed to indicate a normal, i.e., lowsilica, ferrian muscovite (Webb, 1939; 6dman, 1950). X-ray studies, however, indicate that not all true alurgite is twolayer monoclinic in structure; some is three-layer rhombohedral Thus the term alurgite has at various times been used for: (a) a red, high-silica muscovite with minor Fe3 and Mn. (Penfield, 1893); (b) a red ferrian low-silica muscovite (Webb, 1939 and Odman, 1950); (c) a manganian high-silica muscovite (Winchell, 1951); and (d) a three-layer rhombohedral polymorph of (a), discovered by Hendricks and Jefferson (1939) and verified by us on material from St. Marcel, Italy. _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _5__ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __5

ENGINEERING RESEARCH INSTITUTE * UNIVERSITY OF MICHIGAN Because of this confusion, the use of the term alurgite for the high-silica end-member of the muscovite series is also undesirable. Less confusion accompanies the term phengite, which has been generally employed to mean high-silica muscovite. Hypothetical end-members, ferrophengite, picrophengite. h. Rhombohedral phengite.(3R phengite). Differs from 2M phengite (lg) in having the three-layer rhombohedral structure (3R) and 2V = 0~ - low. No well authenticated analysis of alluniaxial material is available. i. Chromian phengite. Cr, with maximum of 0.78% Cr203 (Whitmore,. et al., 1946), for Al. Structure: 2M muscovite. This follows the usage of Whitmore et al. (1946). Synonyms: chromochre, mariposite. j. Rhombohedral chromian phengite. (3R chromian phengite). Presumably chemically similar to Ti, but with the three-layer rhombohedral structure and 2V = 0" - low. No analysis of all uniaxial material available. k. Sericite. Fine-grained muscovite. Structure: 2M muscovite. The term sericite has been used for(a) fine-grained muscovite, either primary or secondary; (b) fine-grained phengite; and (c) hydromusc ovite. Thus it cannot be defined exactly on a chemical basis. It remains, however, highly useful as a general, nonspecific term for fine-grained muscovite whose exact chemical nature is unknown. Synonyms: (including pinitic pseudomorphs). achlusite, agalmatolite, aspasiolite, avalite, bildstein, bonsdorffite, catalinite, cataspilite, cordierite-pinite, cymatolite, damourite (in part), dysyntribite, epileucite, epi-sericite, fahlunite giesickite, gigantolite, gibertite, glimmer, gongylite, helvetan, hygrophyllite, iberite, ivigitite, killinite, lardite, lepidomorphite, liebenerite, lythrodes, margarodite, micarel, micarelle, oncophyllite, oncosine, onkophyllit, onkosin, oosite, pagodite, parophite, pinitepinitoidpolyargite pyknophyllite, pyrargillite, pyrrholite, rosellan, rosellite, _________________________________ 6 _________________________________

ENGINEERING RESEARCH INSTITUTE * UNIVERSITY OF MICHIGAN rosite, shilkinite, sterlingite, talcite, terenite, triclasite, wilsonite. Species 2. Paragonite (NaX)2A14(Si6 A12)8020(OH)4. Structure: 2M probably 2M muscovite. Schaller and Stevens (1941) have pointed out that the series muscovite-paragonite is not completely represented in nature. If intermediate types are discovered, it might be better to regard paragonite as sodian muscovite and reduce it to varietal status. Synonyms: hallerite, natronglimmer, pregrattit, soda mica. Species 3. Roscoelite. K2(V,Al)4(Si6A12)8020(OH)4 Maximum V2C = (ca.) 20%. Structure: 1M. Although roscoelite has previously been regarded as a vanidiferous muscovite, it deserves full species rank because it is structurally distinct (Quarterly Report No. 3). Synonyms: colomite, vanadinglimmer, vanadium muscovite. Species 4. Lepidolite. K2(LiAl)5_6(Si6_7,AA121)8020-21(FOH)53_4 Rb and Cs replace K, in some types in considerable amounts (Rb2O = 3.2% Cs20O = 1.90%, Lundblad, 1942). Small amounts of Mn, Mg, Fe2. Fe3 are normally present. The OH:F ratio varies considerably, and OH may become negligible. Synonyms: irvingite, lilalith, lilalite, Li-phengite, lithia mica, lithionglimmer, lithionit, lithionite, lithionitesilicat, macrolepidolite, microlepidotite, poly-irvingite, scale stone, siderischer-fels-glimmer. Hypothetical end-members: paucilithionite, polylithionite (in part), protolithionite. Varieties. a. Six-layer monoclinic lepidolite.(6M lepidolite) Li20 = (ca.) 4.0 - 5.1%. b. One-layer monoclinic lepidolite. (1M lepidolite) Li20 = 5.1 - 7.26%. c. Three-layer rhombohedral lepidolite. (3R lepidolite) Composition approaches 4b. Due to twinning (?) (Levinson, 19535). 2V = 0-small0.

ENGINEERING RESEARCH INSTITUTE ~ UNIVERSITY OF MICHIGAN d. Three-layer monoclinic (3M lepidolite) LiO2 = 4o1%. One example from Skuleboda, Sweden (Quarterly Report No. 2). e. Manganian-lepidolite. Maximum reported MnO = 7.55% (Shibata, 1952). Structure: probably variable, depending on Li content. f. Magnesian-lepidolite. (cited in Berman, 1937). We are unable to determine if any natural material of this composition has been discovered. g. Polylithionite. (in part). K2Li4A12Si8020(FOH)4. A silicon-and lithium-rich, thus aluminum poor, lepidolite. Structure: 1M. Species 5. Taeniolite. K2Mg4Li2Si8020F4; Structure: 1M. Species 6. Zinnwaldite. K2(Fe21_2Li2-3A12)6(Si6_7 A12-1)020. F3-2, OH1-2)4' The (Al, Fe, Li) group may be considerably deficient. Zinnwaldites are chemically and structurally much more closely related to the biotites than to the lepidolites. No zinnwaldites have been found with the six-layer monoclinic structure so common in lepidolites. Also, the two-layer monoclinic octophyllite structure has been found in zinnwaldite, but not in lepidolite. In fact, there is no sharp natural compositional boundary between zinnwaldite and lithian biotite. If a demarcation is to be made, we believe the line can best be drawn on the amount of Li and suggest that lithium-iron micas with Li >1 atoms per unit cell formula be rebarded as zinnwaldites, those with Li < 1 be placed with the lithian biotites. Synonyms: cryophyllite (in part), lithioneisenglimmer, polylithionite (in part), protolithionite, rabenglimmer. Varieties. a. One-layer monoclinic zinnwaldite (1M zinnwaldite). b Two-layer monoclinic zinnwaldite (2M zinnwaldite). c. Three-layer rhombohedral zinnwaldite (3R zinnwaldite). d. Ferrian zinnwaldite maximum report Fe203 = 10.06% (Shibata, 1952). 8

- ENGINEERING RESEARCH INSTITUTE * UNIVERSITY OF MICHIGAN Species 7. Phlogopite. K2(Mg6Fe2) (Si6A12)8020(OH)4. Na can substitute for K up to nearly K: Na = 1:1 (Harada, 1936); minor Rb, Cs, Ba, and very minor Ca also may proxy for K. Fe2 is almost always present, but Mg predominates greatly over Fe2. Small amounts of Mn, Fe3 and Ti may be present. The Si: tetrahedral Al ratio may be larger than 6:2. There is no well-defined, natural, compositional boundary between ferroan phlogopite and magnesian biotite. Because Fe2 is a strong chromophae, micas of this type even with only a small per cent of Fe are dark colored and are thus commonly classed as biotites. If a division is required, we suggest that where the ratio of Mg:Fe2'4:2, the mineral should be classed as phlogopite. Synonyms: aspidolite barium-phlogopite, barytbiotite, hydrophlogopite, magnesia mica, natronophlogopite, octophyllite, pholidolite, rhombic mica. Hypothetical end-members: fluor-phlogopite, hydroxylphlogopite. Varieties a. One-layer monoclinic phlogopite (1M phlogopite). The most common type. b. Two-layer monoclinic phlogopite (2M phlogopite). c. Three-layer rhombohedral phlogopite (3R phlogopite). d. Manganophyllite. K2(Mg5_4,Mn2-1_ Fe20_0.)6Fe3_lMn30-l (Si6A12)8020. Structure: Generally 1M; some approach a three layer rhombohedral structure. 2M reported by Hendricks and Jefferson (1939). Although some investigators (e.g., Hey, 1950) class manganophyllites as varieties of biotites,: most manganophyllites have little or no Fe2 and only small amounts of Fe3. An exception is a Langban, Sweden, mica analyzed by Jakob (No. 8, p. 157, 1925) which contains 16.94% Fe203. Apparently Mn is present commonly as Mn3, rarely as Mn2 Jakob, (1925). Synonyms: Manganese mica, manganophyll. e. Titanian phlogopite. K2MgsTi(Si6A12)022(0HF)2 (Prider 1939) Fe2and Fe3 are minor. Structure: IM _________________________________ 9 _________________________________

ENGINEERING RESEARCH INSTITUTE * UNIVERSITY OF MICHIGAN Species 8. Biotite K2(Fe2, Mg)6_4(Fe3 Al Ti)o-2(Si6-5A12-35)802o22 (OHF)4_2; Some Na, Ca, Ba, Rb, and Cs for K; Mn for Fe2; F for OH; Mg may be absent. Total F + OH may be very low (Walker and Parsons, 1926). Synonyms- annite, anomite, caesium-biotite, chromglimmer (in part), euchlorite, eukamptite, ferromuscovite, haughtonite,, heterophyllite, hexagonal mica, iron mica, lepidomelane, meroxene, natronbiotite, octophyllite, odenite, odinite, odite, oderite-, pterolite, rhombenglimmer, rubellan, siderophyllite, titanglimmer, titanmica, uniaxial mica, waddoite. Hypothetical end-members: cryophyllite (in part), eastonite, fluor-annite, fluor-biotite, fluor-lepidomelane, fluor-meroxene fluor-siderophyllite, hydroxyl-annite, hydroxyl-biotite, hydroxyl-lepidomelane, hydroxyl-meroxene, hydroxyl-siderophyllite, manganophyllite (in part). Varieties a. One-layer monoclinic biotite (1M biotite) The most common type. b. Two-layer monoclinic biotite (2M biotite). c. Three-layer rhombohedral biotite (3R biotite). d. Six-layer triclinic biotite (6T biotite). e. Twenty-four-layer triclinic biotite (24T biotite). f. Forty-eight-layer triclinic biotite (48T biotite). So A. Forman, Bureau of Mines, Ottawa, Canada, indicates that he has found a forty-eight-layer triclinic form (personal communication). g. Calcian biotite. A biotite from Kaiserstuhl, Germany, has 8.17% CaO (Daub, 1913). Structure unknown. The validity of calcian biotite as a major variety is doubtful. The existence of Ca in the biotite structure has been challenged by Jacob (1929). Several specimens labelled calicobiotite, from Italian localities, have been found to have the 1M structure. h. Ferroan biotite. Mg is very minor or absent, Fe is present mainly as Fe2, Synonyms: siderophyllite, lepidomelane (in part). ___________________________ 10 _____________

ENGINEERING RESEARCH INSTITUTE * UNIVERSITY OF MICHIGAN i. Manganian-biotite Mn as much as 1 atom per unit cell formula. Fe present as Fe2 or Fe5. j. Ferrian biotite. K2(Fe2,Mg)3_4Fe32_3(Si6,A1,Ti)8020-2. Synonyms: ferribiotite, lepidomelane (in part). Lepidomelane is commonly employed for iron-rich biotite, but the term has been used to embrace biotites rich in Fe3, those rich in Fe2 and those with relatively large amounts of both Fe2 and Fe3 (Heinrich 1946). k. Lithian biotite. K2(Fe2,Mg)5 (LiAl,Fe3)1(Si7,Al)8020 (OH,F)4. 1. Titanian biotite. K2(Fe2,Mg3)5Ti(i6,Al2)8 22(OHF)2. Synonyms: ferrititanbiotite, ferriwotanite, titanbiotite, titanobiotite, wodanite, wotanite. Both titanian biotite and titanium pholgopites are relatively poor in Fe3 and also are very low in OH and F. Hydrous Micas Because most investigators class these minerals with the clay group, their crystal chemistry is not considered here. However, it is interesting to note that a new interpretation (rrown and Norrish, 1952) of the chemistry of one of the species in this group, hydromuscovite, postu-.lates the replacement of K by oxonium (hydronium) ions H30+. Species and varietal names included in this group are: bastonite, brammallite, bravaisite, buldymite, damourite (in part), goeschwitzite, grundite, gumbelite,, hydrobiotite, hydro-mica, illite, metasericite, Mg-illidromica, rastolyte, sarospatakite, sarospatite, sericite (in part) sodium-illite, Voigtite. Micas of Indeterminate Status 1. Euphyllite - near (Na,K)A13Si3010(OH)2; may be a mica intermediate between muscovite and paragonite; or brittle mica or perhaps a mixture. 2. Mahadevite - near (K,Na)o.97(Al,Fe,Mg)2,66(SiAl)4(0O0H)12; supposedly between muscovite and phlogopite in composition. _11

ENGINEERING RESEARCH INSTITUTE ~ UNIVERSITY OF MICHIGAN 3. Manandonite - a borosilicate of Li and Al closest to lepidolite in composition; Li4All4B4Si6029(OH)24(?)-possibly not a mica. 4. Leuco.phyllite - a high silica phengite - perhaps a mixture. 5. Anthrophyllite - a "mica (?)" (Hey 1950, p. 283). Other Varietal Names Anhydr omus c ovite Baddec kite Anhydrob ot ite Bauerite Metabiot ite _____________________________ 12 ______________

REFERENCES Bauer, L. H., and Berman, H. (1933), Barium-muscovite from Franklin, N.J.: AImMineral., 18, p. 30. Berman, H. (1937), Constitution and classification of the natural silicates: Am. Mineral., 22, pp. 342-408. Brown, G., and Norrish, K. (1952), Hydrous micas: Min. Mag., 29, pp. 929-932. Clarke, F. Wo (1889), A theory of the mica group: Amer. Jour. Sci., 138, pp. 384-393. Daub, R. (1913), Beitrage zur Kenntnis der Kontaktmineralien aus dem korrigen Kalke des Kaiserstuhls. Inaug.-Diss. Freiburg i. Br. 1912: Neues Jahrb. Min. Geol. und Paleon., 1913, (1), pp. 214-217. Doelter, C. (1914), Handbuch der Mineralchemie: vol. 2, part 2, p. 442. Eskola, P. (1914), On the petrology of the Orijarvi Region in southwestern Finland: Bull. Geol. Comm. Finland, No. 40, p. 37. Ellsworth, H. V. (1932), Rare-element minerals of Canada: Canada Geol. Survey, Econ. Geol. Ser. No. 11, p. 266. Harada, Z. (1936), Chemische Analysenresultate von japanischen mineralien: Jour. Fac. Sci. Hokkaido Imp. Univ., Sapporo, Japan, vol. 3, ser. 4, pp. 221-362. Heinrich, E. W., (1946), Studies in the mica group; the biotite-Dhlogopite series: Amer. Jour. Sci., 244, pp. 836-848. Hendricks, S. B., and Jefferson, M. E. (1939), Polymorphism of the micas: Am. Mineral., 24, pp. 729-771. Hey, M. H. (1950), An Index of mineral species and varieties arranged chemically: British Museum, London. Jakob, J. (1925), Beitrige zur chemischen Konstitution der Glimmer. I. Mitteilungo Die schwedischen manganophylle: Zeit. Kristo, 61, pp. 155-163. (1929), Beitrige zur chemischen Konstitution der Glimmer. V. Mitteilung. Die Muskovite der Pegmatite. II. Tiel: Zeit. Krist., 69, pp. 403-410. Kunitz, W. (1924), Die Beziehungen zwichen der chemischen Zusammensetzung und den physikalish-optischen Eigenschaften innerhalb der Glimmergruppe: Neues. Jahrb., Beilage-Band, 50, ppo 365-4135 Levinson, A. (1953), Studies inthe mica group; Relationship between polymorphism and composition in the muscovite-lepidolite series, Am. Mineral., in press. 13

Lundblad, B. (1942), Optical studies of the analyzed micas from Varutrqsk, Minerals of the Varutrask Pegmatite XXXII~ Geolo Foren. Forh., 64, pp. 55-60. Odman, O.H. (1950), Manganese mineralization in the Ultevis District, Jokkmokk North Sweden~ Part 2 Mineralogical Notes~ Sveriges Geol. Undersokning, Ser. C, Arsbok, 44, No. 2. Pagliani, G. (1937), Sur una mica della miniera di talco delle Fontane (Valle della Germanasca): Atti. Soc. Ital. Sci, Nat. Mus. Civ. Milano, 76, pp. 13-16. Penfield, S. L., (1893), On some minerals from the manganese mines of St Marcel, in Piedmont, Italy: Amer. Journ. Scio 46, pp. 288-295 (1893). Prider, R. T. (1939), Some minerals from the leucite-rich rocks of the West Kimberly area, Western Australia: Min. Mag. 25, pp. 373-387. Ramsdell, Lo S. (1947), Studies on silicon carbide: Am. Mineral., 32, pp. 64-82. Schaller, W. T. (1930), Adjectival ending of chemical elements used as modifiers to mineral names: Am. Mineral., 15, pp. 566-574. (1950), An interpretation of the composition of high-silica sericites: Min. Mag., 29, pp. 405-415. and Stevens, R. E. (1941), The validity of paragonite as a mineral species: Am. Mineral., 26, pp. 541-545. Shibata, H. (1952), Mineralizations in granite-pegmatites in Japan and Korea. Part III: Science Reports, Geol. Min. Inst., Tokyo Bunrika Daigaku (Tokyo Univ. of Lit, and Sci.) Ser. C, vol. 2, no. 12, p. 161-164. Starkl, G. (1883), Ueber neue Mineralvorkommnisse in Oesterreich: Jahrb. der k.-k. Geol. Reichsanstalt, Vienna, 33, pp. 653-656. (cited in Schaller 1950). Stevens, R. E. (1946), A system for calculating analyses of micas and related minerals to end members: U. S. Geolo Survey Bull. 950, pp. 101-119. Tschermak, G., (1878), Die Glimmergruppe: Zeit. Krist., 3, pp. 122-167. Walker, T. L., and Parsons, A. L. (1926), Minerals from the nepheline syenite area, French River, Ontario: Univ. of Toronto Studies, Geol. Series, No. 22, pp, 5-14. Webb, R. W. (1939), Investigation of a new occurrence of alurgite from California: Am. Mineral., 24, pp. 123-129. Whitmore, D. R. E., Berry, L. G., and Hawley, J. E. (1946), Chrome micas: Am. Mineral., 31, pp. 1-21. 14

Winchell, A. N. and Winchell, Ho (1951), Elements of optical Mineralogy. Part II. Descriptions of minerals, 4th ed.o ppo 365-377, New York. Wllfingg E. A. (1886), Untersuchung zweier Glimmer aus den Gneissen des Rheinwaldhorn-Massivs. Graubunden: Ber. Deutschen Chemo Gesellschaft., 19, pp. 2433-2438. 15