三波川変成岩中のブラウン鉱は多くの場合紅れん石と石英と共生する。今回研究を行なった試料は石英だけと共生するもので,いいかえると過剰のシリカ存在下で再結晶化が行なわれたものである。母岩の変成度は緑れん石角閃岩相を示すが,このような条件下で生成したブラウン鉱の化学組成を検討した結果,理想式に近いシリカ組成を有することが分った。さらに,広域変成岩中のもの2ヶと接触変成作用をうけたマンガン鉱床産の1ヶの分析を行ない,文献からえられた資料とともに再検討を行なった結果も同じであった。すなわち,Muan(1959)によって指摘されたような多量のMnとsiの置換は生じないと考えられる。

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Mineralogical properties of large single crystals of Zn and Mg-bearing manganoan magnetite from Kawara-Sannotake, were described. The magnetite crystals which are 2.5 cm in maximum diameter, take the basic form of rhombic dodecahedron with frequent combination of smaller face of o(111) and unusual pyramidal face m(311). A typical example of chemical formula for the magnetite crystals, determined by electron microprobe analysis is given below.
(Zn_0.40²⁺Mn_2.45²⁺Fe_5.15³⁺)_8.00[Mg_0.47³⁺Fe_4.65²⁺Fe_10.87³⁺]_15.99O_32.00
A precise determination of lattice parameter for this magnetite gave 8.4387 Å, which is larger than that of foliated magnetite of ordinary composition from the same locality, 8.3940 Å. Specific gravity is 5.089 measured and 5.080 calculated. In polished sections of the manganoan magnetite crystal, pyrrhotite, chalcopyrite and quartz can be observed as inclusions. Reflectivity in air for this crystal seems to be somewhat darker than that of the foliated magnetite. Its intensity of magnetization at 19°C under external magnetic field of 10 K·Oe attains 93.1 emu/g, and the theoretical value based on the cation distribution in its crystal structure at 0°K is calculated to be 106.5 emu/g, whereas the ordinary magnetite shows 96.7 emu/g. Curie temperature of the manganoan magnetite is 466°C, which is lower than that of ordinary magnetite, 580°C. DTA experiments carried out in air show two exothermic reactions. The lower temperature peak at 300°C is small but sharp, and the other exothermic plateau starts rapidly from its Curie temperature.
The Zn and Mg-bearing manganoan magnetite crystals are supposed to be generated by reaction of locally pre-existing iron-manganese ore formation with hydrothermal solution, which involves Zn, Mg and (Sn ?), etc., as the later different mineralization from the skarnization widely developed in this area.

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Rhodochrosite from the Oe and Inakuraishi Mines situated in south-western Hokkaido, which consist of veins of the epithermal type developed in the Miocene formation and intrusive quartz-diorite, occurs in various kinds of colors from rose pink to pale purple and gray showing the crustified banding structure, sometimes in association with the bands of sulfide minerals. The seven kinds of rhodochrosites in color as given in Table 1 were analysed by EPMA on their chemical composi-tions. The measured values were calculated by the Bence and Albee method, and analytical data were obtained as shown in Table 2 and Fig. 5. The composition ranges of rhodochrosite from both mines are represented in Fig. 6. The maximum amounts of CaCO₃, FeCO₂ and MgCO₃ moles in the rhodochrosite are 30%, 370% and 9% respectively. Also the changes of chemical composition in the bandings of rhodochrosite ore associated with calcite, quartz an sulfide minerals are shown in Fig. 7.

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　今回検討した層状マンガン鉱床に伴うjacobsiteの化学組成および共存する酸化鉱物との固溶関係をまとめると次のようになる。　1)　jacobsiteは,一般に相当量のAl, Ti, Mgなどの元素を含み,広い固溶領域を有する。　2)　一般にgalaxite分子および"Mn₂TiO₄"分子を固溶する場合が多く,それぞれ最高25および36mol.%程度に達する。　3)　上記の"Mn₂TiO₄"分子は,iwakiite中にも最高44mol.%程度固溶しており,天然では普通に見られる固溶成分である。

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Two managanoan phlogopites with reverse pleochroism have been found in the managanese deposits of Taguchi and Nodatamagawa mines. The mineral shows the reverse pleochroism, namely, X=reddish brown or brown, Y=Z=light yellow. Chemical analyses and Mössbauer spectra indicate that the reverse pleochroism is due to the substitution of Fe³⁺ atom for Si and Al atoms in the tetrahedral site.

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The chemical analyses were made on twenty four cryptomelanes, five manjiroites and two hollandites from northeastern Japan after the confirmation of their purity though X-ray and thermal studies. These results and analytical data on many for eign samples lead to the general formula A_1±xMn₈O₁₆·nH₂O, where A represents large ions such as K⁺, Na⁺, Ba²⁺, Ca²⁺, Pb²⁺etc., Mn is chiefly Mn⁴⁺ with a small quantity of medium and small-sized ions such as Mn²⁺, Mg²⁺, Fe³⁺, Al³⁺ etc. n is between 0 to 2 and the average 1.2. The value of 1+x ranges between 1.28 and 0.17 and the average is 0.88. X-ray diffraction patterns of Japanese cryptomelane-manjiroite series can be indexed in terms of a body-centered tetragonal unit cell. Lattice constant a₀ of this series varies appreciably but somewhat systimatically with the variation in the Na/Na+K ratio, whereas c₀ varies little.
Heating experiments of cryptomelane, manjiroite and hollandite in air established the following process of thermal transformation:
cryptomelane manjiroite hollandite → approx. 600°C α-Mn₂O₃ (bixbyite) → approx. 900°C tetr. Mn₃O₄ + X phase. (hausmannite)
In th case of cryptomelane X phase had been considered to be the remnant of the small amount of untransformed cryptomelane, but the present study shows that the X phases of three heated minerals were the compounds belong to the systems K₂O-, Na₂O- and BaO-manganese oxide respectively.

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Four manganese borate minerals, jimboite, wiserite, sussexite, and Mineral X of Epprecht et al. (1959) have been found in seventeen bedded manganese ore deposits in Japan. Their principal mineralogical properties and mineral associations are given to present their diagnostic features and the characteristics of manganese ores comprising them. The manganese borates occur as layers conformable with bedded textures of ores, minute veinlets cutting them, or minor interstitial bodies among associated minerals. Ore minerals associated with them include rhodochrosite, jacobsite, sonolite (or alleghanyite), alabandite, jacobsite, galaxite, hausmannite, tephroite and gageite, these being characteristic in low silica and higher grade manganese ores. The occurrences suggest the simultaneous concentration of boron with manganese, these elements being considered to have been released from basic magma after the reaction with sea water.

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Chemical analyses of thirty four manganese-bearing amphiboles from Japan are reviewed from the standpoints of chemical composition and classification. According to the nomenclature approved by the IMA Commission on New Minerals and Mineral Names, clarified that amphiboles are classed as four groups, i.e., (a) iron-magnesium-manganese amphibole group (five tirodites and six dannemolites), (b) calcic amphibole group(five actinolites, one actinolitic hornblende and one ferrohornblende), (c) sodic-calcic amphibole group (four winchites and two richterites), and (d) alkali amphibole group (six magnesioarfvedsonites and one kôzulite). Winchite is defined as sodic-calcic amphibole in which (Na+K)_A<0.50, Si in the standard cell between 7.50 and 8.00, and Mg/Mg+Fe²⁺ between 0.50 and 1.00. The composition of Noda-Tamagawa green amphibole, Kotamagawa richterite and Hijikuzu magnesioriebeckite, which were described previously by Nambu et al., satisfies the definition of winchite, and Yoshimura's riebeckrichterites are recognized as richterite (yellow-black variety) and magnesioarfvedsonite (yellow-brown variety). Judging from the fact that Mn substitutes for Mg and Fe²⁺ in magnesioarfvedsonites in considerable excess of the ideal composition, it is most probable that magnesioarfvedsonite and kôozulite form a complete isomorphous series.

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Manganese-bearing pyroxenes from Japan were reviewed from a chemical point of view. Twenty analytical data in the literature and two new ones indicate that they are classified into one kanoite, two johannsenites, twelve ferrosalitehedenbergite series minerals and seven aegirine-aegirine-augite series minerals. Two minerals of johannsenite and hedenbergite are isostructural and probably form a continuous solid solution series, while naturally occurring ferroan johannsenite and johannsenite show that a narrow compositional gap separates these two minerals. MnO content in Japanese aegirine and aegirine-augite varies from 3.260% to 8.18%, and this fact will indicate that the solid solubility of johannsenite comopsition in these minerals are limited. The chemical composition of urbanite is so variable within the aefirine-aegirine-augite series that urbanite can be classed as the manganoan aegirine or manganoan aegirine-augite.

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Manganese bearing carbonate, sulfate and niobate minerals were analyzed by ICP emission spectroscopic technique with good reproducibilitis. The supression effect of acids were removed by keeping the acid concentrations the same in both sample and standard solutions. So far as our studies have concerned, in the ICP analysis of manganese minerals, all interferences caused by coexisting elements were found to be additive. The corrections were made by substracting the emission intensity of a diverse element at the wavelength of analyzing elements from the total emission intensity. Analysis of carbonate and sulfate minerals : About 10 mg of weighed sample is dissolved in dilute hydrochloric acid and diluted with water to 20-50 ml, and emission intensities are recorded. The concentration of analyzing elements are determined by the calibration curve method. Reproducibilities calculated from the seven repeated runs of the analysis for a rhodochrosite sample were as follows : MnO wt. %, 48.2% (S. D. 1.38%), FeO 8.86% (S. D. 0.56%), CaO 1.62% (S. D. 2.07%), MgO 1.05% (S. D. 1.08%), ZnO 0.033% (S. D. 13.1%). The procedure is also applicable to acid soluble manganese oxide minerals. Analysis of niobate minerals : About 10 mg of weighed sample is dissolved in the mixed acid of hydrofluoric and sulfuric, evaporated to the strong acid fume and cooled.The residue is taken in dilute sulfuric acid containing hydrogen peroxide, and diluted to 100 ml and then emission spectroscopic intensities are collected. Results of analyses of four columbite samples from different localities are given in tables together with specific gravity data and unit cell parameters.

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Intracrystalline cation distributions in solid solution of olivine structure, (Mn, Mg, Fe)₂SiO₄ were reviewed and discussed based on the results determined by X-ray and Mössbauer studies. A natural forsterite from a xenolith in a kimberlite showed a slight preference of Fe for the smaller M1 sites (K_D=1.14). Any significant effect of pressure on the intracrystalline cation distribution was not detected. A magnesian tephroite from a contact-metamorphosed manganese ore deposit showed a strong preference of Mn for the larger M2 sites (K_D=0.0616), and after heating at 1000°C for 3 weeks, its cation distribution changed to be a more disordered type (K_D=0.279). In Mg-Mn olivine, therefore, the ordering of Mn for M2 sites decreases with increasing temperature. In Mg-Fe olivine, the luck of cation ordering in metamorphic olivine can be explained by th assumption that the standard Gibbs free energy differece, ΔG°, for the cation exchange reaction between M1 and M2 sites is nearly zero in the range over the metamorphic temperatures.

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Many kinds of phase transformations in pyroxinoids in the system, CaO-MnOFeO-SiO₂, have been discussed on their crystal chemical and thermodynamical respect.
Mono-phase transition in CaSiO₃ between wollastonite and pseudowollastonite is caused by changing configurations of octahedral cations and results in the transformation from a chain silicate to a ring silicate. Since a free energy of pseudowollastonite bearing other divalent cations than calcium seems to increase with those contents, wollastonite having more than a certain amount of them is directly melt without the transition to pseudowollastonite.
Polytypic transformation between wollastonite (1T) to parawollastonite (2M)was found to be induced by thermal sheer stress in the slab structure, and a certaintype in 3T and 7T polytypes are thermodynamically stable.
A fanction G(X)₀=xG_1T+(1-x)G_2M-f(x)T S(x)_slab represents a free energy of the ordered slab structure and the last term takes a part to reduce th energy of the structure compared with that of a disordered mechanical mixed structure.
Intracrystalline cation self diffusion in a octahedral bands causes the change of periodicity of silicate chains and bring about phase transition from rhodonite to bustamite.
Clinopyroxene, ferroan johannsenite and manganoan-hedenbergite, made a thermal transition to bustamite at 1050°C for 120 hrs, in which a topotaxtic transformation between them was observed. On the basis of the study of stability regions of those phase as a function of temperature, schematical phase diagram has been discussed in the join between CaMnSi₂O₆ and CaFeSi₂O₆.

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The stable polymorphs of MnGeO₃ are orthopyroxene type (Phase I), clinopyroxenetype (II), ilmenite type (III) and perovskite type (IV) in the order of pressureincrease. The crystallographic data and crystal structures of the polymorphs aredescribed except for the perovskite type, the structure of which has not been accuratelydetermined. These structures areE compared with the structures of similargermanates and silicates of different metals rather than Mn and the characteristicsof the ilmenite type (III) of MnGeO₃ are discussed.

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Manganese-bearing layer silicates form a large family of layer silicates characteristic of having complex structures. This is because dimensional misfit between the octahedral-and tetrahedral-sheets is in general so large that tetrahedral sheets sensibly change, according to the degree of misfit, their configuration so as to adapt themselves to the adjoining octahedral sheets. Various mechanisms of evading misfit to form a structure are described and discussed based on four examples : (1) bementite, Mn₇Si₆O₁₅ (OH)₈, P 222₁, a=14.5 Å, b=17.5, c=7.28×4(=29Å), Z=16. A half set of the six-membered rings in the tetrahedral sheets of the structure, which is similar to that of pyrosmalite, is inverted relatively to the remaining half. (2) caryopilite, the so-called manganese serpentine. A peculiar electron diffraction pattern characteristic o this mineral and sub-microscopic texture observed by electron microscope are described. (3) pyrosmalite-group minerals. The pyrosmalite structure refined, stacking sequences of various polytypes are given. (4) ganophyllite, (K, Na, Ca) Mn₈(Si, Al)₁₂ (O, OH)₃₂(OH)₄.nH₂O (n×4-6), A2/a, a=16.60, b=27.13, c=50.18, β=93.9600, Z=24. The structure is described based on the subcell structure (a'=a/3, b'= b/2, c'=c/2, β'=β, I2/a). The manganese octahedral sheet is sandwiched by two tetrahedral sheets, each is in fact consisting of triple chains; the structure thus ogers an elegant example of minimizing misfit. The interlayer cations are each eight coordinated at the edges of the triple chains. The superstructure is caused by an ordering of the interlayer cations and water molecules due to the site preference of Al in the triple chains.

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Fluor-sonolite, -alleghanyite, and -norbergite have been synthesized fron the conventional. hyrothermal technique in 1 or 2 kb water vapour pressures at 350° to 700°C.
Alleghanyite and norbergite are easily produced as beautiful pink grains of single phase from the mixture of carbonate, silica-gel, and manganese fluoride. Single phase of pink sonolite has been found incidentally in the hydrothermal product from a starting material of manganhumite composition. From the indexed powder data referred to those of chondrodite group, the calculated lattice dimensions are as follow; for sonolite a=10.653A, b=4.883A, c=14.312A, and β=100°44'; for alleghanyite a=10.706A, b=4.868A, c=8.200A, and β=109°02'; for Mn-norbergite a=10.771A, b=4.868A, and c=9.297A.
Some phase relations in the system MnO-MnF₂-SiO₂ and the role of fluorine fugasity are discussed in some detail.

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Komano-yu hot spring near Komaga-dake, Hokkaido, Japan is especially interesting, because manganese hydroxide is found in the process of deposition. The problem of whether the frequency and amount of some minor elements with which they are associated in the stratified deposits in Tertiary formations, deep sea nodules and recent bog ore from Komano-yu hot spring differ sufficiently in relation to different sources of the manganese, and separation of manganese from iron in the process of deposition of bog ore are discussed. Stable isotope ratios of hydrogen of water and manganese hydroxide mineral from Komano-yu hot spring were measured. The hot spring water probably form from local meteoric water of this area.

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Japanese bedded manganese ore deposits are classified into two types, those in Palaeozoic and Mesozoic geosynclinal sediments. and those in Neogene neritic sediments distributed in Green Tuff region. The former geochemically and stratigraphically shows affinities to metalliferous deposits of hydrothermal origin associated with modern spreading center, except ore-forming minerals. The most common ore-forming minerals of nonmetamorphosed or weakly metamorphosed deposits belonging to this type arc rhodochrosite with small amounts of hausmannite. The ores of metamorphosed deposits are mainly composed of silicate minerals such as rhodonite, pyroxmangite and tephroite which were probably changed from rhodochrosite. The deposits closely related to basic rocks are characterized by the occurrence of braunite in the siliceous ore. The latter is apparently the products of hot spring activities related to the middle Neogene volcanism of Green Tuff movement and the ores are mainly composed of manganese dioxide minerals and manganite. Besides the bedded deposits, rhodochrosite veins are also found in some districts of Green Tuff region. These manganese mineralization probably originated as a result of the mobilization of manganese from the bedded ore deposits in the pre-Cenozoic basement during circulation of thermal water. Investigation of the geochemistry of manganese, sedimentary environments and igneous activities lead to the conclusion that original minerals of both types were hydrous manganese dioxide minerals and/or manganite precipitated primarily after discharge of the thermal solutions through the sea floor. This hypothesis means that rhodochrositehausmannite assemblages characterizing the bedded manganese ore deposits in older geosynclinal sediments were the products of carbonitization of hydrous manganese dioxide minerals in the process of diagenesis, and that manganese silicate minerals were produced in the process of metamorphism.

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