Tosudite specimens occurring as monomineralic veinlet and as a prominent constituent of pottery stone in the Rokuro deposit, Ehime Prefecture, have been examined by X-ray, chemical, thermal and infrared methods. The basal reflections are very close to an exact integral series : the mean value of d(001) is 29.41 Å in natural state, and expands to 32.10 Å by glycerol solvation after saturation with Mg. The value of d(060) is 1.489Å. Taking the exchangeable cations into consideration, a reasonable structural formula is given as follows; chlorite layer : [Al_1.99Fe³⁺_0.03 Mg_0.01Li_0.84K_0.15Na_0.01(NH₄)_0.03](OH)₆·Al_2.00(Si_2.89Al_1.11)O₁₀(OH)₂, smectite layer : [Al_0.12Mg_0.01K_0.01(NH₄)_0.01]·5.0H₂O Al_2.00(Si_3.59Al_0.41)O₁₀(OH)₂.The chlorite layer is close to an ideal cookeite composition. However, small amounts of K incorporated into the interlayer octahedral sheet seem to be essential to construct the chlorite layer. Interlayer Al in the smectite layer is presumably combined with hydroxyl (hydroxyl Al ion), which is correlated to the distinctive endothermic reactions at 350 and 410°C. The infrared OH absorption bands and the refined z-parameters of atomic planes are also discussed in regards with accommodation of K ions in the structure of Li-tosudite.

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Structural rearrangements for dioctahedral smectite after thermal treatment were investigated. The notable structural changes accompanying removal of interlayer water are contraction of basal spacing, migration of interlayer cation into silicate layer and expansion of b-parameter. The important factor affecting the migration of interlayer cation is considered to be turbostatic stacking of adjacent silicate layers. The dehydroxylated structures of octahedral sheet are similar to those of other dioctahedral clay minerals having 2:1 layer structure, that is, removal of 2OH- as H₂O and relocation of residual O^2- to the same level as that of the octahedral cations.

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The expansion properties of expandable layer in illite/smectite randomly interstratihed clay minerals (I/S) occurring in diagenetic alteration have been directly evaluated by behavior tests (expansion tests) using X-ray diffractometry. The behavior tests have been performed after following preparations : (1) ethylene glycol solvation ; (2) K-saturation and ethylene glycol solvation ; (3) Li-saturation, heating and glycerol solvation (Greene-Kelly test). The results of behavior tests for glycolated samples (unsaturated and K-saturated samples) suggest that smectite layer in I/S convert into high-charged one with increasing percentage of illite layer (I%). The results of Greene-Kelly test indicate that the expandable layer in I/S at early stage of illitization possesses both tetrahedral and octahedral charges, and that the amount of smectite layers having tetrahedral charge decrease with increasing I%. From the results of Greene-Kelly test, it is considered that the smectite layers having tetrahedral charge convert into illite layer selectively. The results of these behavior tests suggest that tetrahedral substitution of smectite layer is more effective in the illitization process than increasing the total layer charge.

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Montmorillonite has been classified into Cheto-type and Wyoming-type, on the basis of their heating products. In order to test the validity of this criterion, montmorillonite samples were exchanged with various cations such as Na, K, Ca, and Mg ions, and their heating products were examined. It is easily confirmed that (1) Mg and Ca ions added are very effective for the formation of high quartz phase, (2) Na and Mg ions are effective for the formation of cristobalite phase, and (3) K ion is effective for the formation of spinel phase. Changes in X-ray powder pattern with heating temperatures suggest that high quartz phases formed are a kind of solid solutions, MgO-SiO₂-Al₂O₃ or CaO-SiO₂-Al₂O₃. All the results obtained show that the heating products do not depend on the characteristics of constituting layer sheets, but those of exchangeable interlayer cations. A factor analysis was also applied to estimate quantitatively the individual effect of cations including alkali metal, alkali earth metal and transition metal ions for the formation of various phases.

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Crystal structure of microcrystal KBSi₃O₈ less than 30 μm was successfully determined by the direct method to X-ray three-dimensional diffraction data. Based on revised structure refined to R = 4.0 and Rw = 3.1% of its 386 observed reflections, it is found that KBSi₃O₈ is not isostructural with reedmergnerite NaBSi₃O₈, but with danburite CaB₂Si₂O₈, . Both micro-Raman and Infrared instruments have also proved to be extremely useful in determining the partial structure of some crystalline samples only a few 10 μm across. Furthermore the application of the Gandolfi camera to RIGAKU X-ray Micro Diffraction Unit with curved PSPC/MDG system is successful in measuring the X-ray diffraction pattern of a single microcrystal which is identical to that of a powder sample.

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The kaolin clay occurring at Djebel Debbar has been used as an important plastic raw material for the production of pottery in Algeria. Its chemical and mineralogical properties, and their influences on slip conditioning, pottery shaping and fired properties were investigated. The principal constituent of the clay was halloysite (10 Å) with a tubular morphology and particle distribution rich in colloidal size particles. In the kaolin deposit, high-grade part with SiO₂/Al₂O₃ ratios in the range from 1.90 to 2.00 was studded with variety size of blocks in the low grade region. The amount of the high-grade ores occupy about 10 to 20% of the output, and the rest are lowgrade ores. They are dark-colored due to the coexisting manganese compounds, calcite, alunite, etc.. The main contaminants are lithiophorite with relatively high Li content, and fine aggregates of colloidal particles. The impurities of Mn amounted to several % as MnO₂ can be removed easily with reducing agent such as sodium dithionite. The slurry of the body system containing the halloysite clay was rather difficult to disperse by the conventional deflocculants, because of much amount of electrolytes from the raw materials and the hard water used. Furthermore, the colloidal particles in the system are in significant amounts resulting in very large viscosity unusable to the shaping, or requiring much water content. Surface properties of the very fine halloysite particles were of benefit to the dry strength and to the rheological feature for plastic formation of the body. The slip rendered the rheological properties available to both slip casting and jiggering by lowering the clay content to 12% and by using barium carbonate, sodium salt of humic acid and sodium silicate as defloccurants. Barium precipitated sulfuric ions and humic acid played an important role, in forming complexes with the polyvalent metal ions and to disperse manganese particles homogenously into the whole body. The clay containing the manganese compounds lowered the vitrification temperature and water-absorption of the fired body.

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Mineralogical aspects concerning the formation mechanism of illite which was produced from precursor smectite in nature are reviewed briefly. Interstratified structures of intermediate illite/smectite (I/S) products in the smectite illitization are distinguished from differences in permeability and porosity of original rocks ; I/S in more permeable rocks transforms discontinuously from a random to an ordered structure, and I/S in less permeable rocks transforms continuously so that a smectite-smectite transition probability decreases gradually. Morphology of I/S grains is also distinctive between both cases. These observations reveal that there are apparently two distinct mechanisms of smectite illitization : one is a mechanism which is dominantly controlled by dissolution of smectite and nucleation and growth of illite and the other is a mechanism dominantly controlled by cation-substitutions within an intact 2:1 silicate layer of precursor smectite. Dissolution and growth processes are not prominent in the latter mechanism. The apparently different mechanisms of illite formation observed in nature are controlled by material flux in relation to the porosity and permeability of rocks.

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The mode of occurrence of clay minerals and the interaction between hot waters and wall rocks in Arima and Takarazuka have been investigated by X-ray powder diffraction, microscopic observation and chemical analysis. The alteration halo can be divided into three zones, such as, zone I (chlorite-mica zone), zone II (silica zone) and zone III (mica-kaolinite zone). Low, medium and high-temperature waters are mainly located in zone I, II and III respectively. Calcite veinlets are present in drilling cores of zone I and II. The pH values of hot waters in zone II calculated on the basis of the calcite-brine equilibrium equations are higher than those in zone I. Partial CO₂ pressure of hot waters are almost constant, indicating a 3.8 atmospheric pressure in zone I, and a 4.9 atmospheric pressure in zone II. The most important factor controlling the chemical composition of hot waters seems to be the calcite-brine equilibrium in wall rocks.

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Altered volcanic rocks are distributed in the Kuwanokizuru area, Hitoyoshi City, Kumamoto Prefecture. Constituent minerals in the altered rocks are smectite, mixed-layered mica/smectite, mixed-layered chlorite/smectite, chlorite, kaolinite, pyrite, quartz and α-cristobalite. Distribution of clay minerals in this area could be divided into two zones, mixed-layered mica/ smectite zone and smectite zone. In the mixed-layered zone, mixed-layered mica/smectite having high % of mica is present at two places. Furthermore, smectite % of this mixed-layered mica/smectite decreases and its Reichweite changes from 1 to 3, from the margin toward these places.

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The Kawarage and Doroyu areas, where a geothermal field has been expected, are located in the southern part of the Yuzawa city, Akita Prefecture. Hotsprings, fumaroles and altered haloes formed by chemically geothermal fluids are found in these areas . The purpose of this study is to clarify the distribution and mineral associations of the alteration zones in both area. The results are as follows.1. The Kawarage area. The dimension of the alteration zone is about 1.5 and 0.5 Km along NW-SE and NE-SW, respectively. Silicified zone is widely spread around the Kawarage Sulfur deposit, and thinly enveloped by an argillized zone. The alteration minerals arranged from center to outer portion are sulfur, silica minerals, alunite, and montmorillonite. The amounts of quartz vary in each sampling piont, but quantitative analysis by X-ray diffraction method reveals that weight percentage of quartz is highest in the silicified zone.2. The Doroyu area. In contrast with The Kawarage area, the alteration zone in the Doroyu area has a smaller dimension of 0.5 and 0.2 Km wide, along NE-SW and NW-SE, respectively. It is composed of a narrow silicified zone and a wide argillized zone. The minerals in alteration zone distributed from its center to outer boundary are sulfur, silica minerals, alunite, kaolinite, and montmorillonite.

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Phyllosilicates were present in the volcanic ashes from several 1982-1983 eruptions of Kusatsu-Shirane Volcano . Pyrophyllite, kaolin and smectite were present as major clay minerals. Hydrothermally altered rocks collected from the western flank showed that, the basement rocks of this volcano were altered to form silica minerals, alunite and various clay minerals such as pyrophyllite, kaolin and smectite. The presence of pyrophyllite in the volcanic ashes indicates that the explosions probably have taken at a depth corresponding to the basement rocks. On the other hand, samples of air-fall tephra from 1897 and 1925 eruptions contained little or no pyrophyllite suggesting that these explosions likely occurred in the volcanic rocks of Kusatsu-Shirane Volcano. Based on the distribution and amounts of clay minerals in the volcanic ejectas, the depth of explosions during repeated eruptions may be inferred.

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Tsubo-ishi, a weathered pebble having an iron-rich spherical crust on the surface and clay materials in the core, was collected in a conglomerate found in the Shemmei Pass area, Gifu Prefecture. The conglomerateis composed of pebble sized and small fragments of chert and embedded in a matrix of clay materials. Occasional pebbles of mudstone, sandy tuff and granite are also found but they are usually weathered and changed to clay. On the other hand, the crust of Tsubo-ishi is composed of goethite and chert granules, whereas the core is dominantly mixture of kaolin minerals with minor mica clay minerals and quartz. This report shows some mineralogical data on Tsubo-ishi and describes its mechamism of formation.

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In order to investigate the genesis of stevensite experimentally, naturally occurring okenite was treated hydrothermally with 0.5 mol/l magnesium chloride solution and with basic magnesium carbonate for Mg (in basic magnesium carbonate)/Si (in okenite) molecular ratios ranging from 0.1 to 1.5. As a result, okenite was altered to “hydrated talc” by treatment with magnesium chloride solution. On the other hand, it was altered to stevensite (Mg/Si = 0.3-0.5), and “hydrated talc” and serpentine (Mg/Si = 0.75-1.5) by basic magnesium carbonate treatment. Furthermore, when sodium hydrogencarbonate was added to the reaction system, larger amount of stevensite (Mg/Si =0.1-1.0) and serpentine (Mg/Si = 1.5) were obtained. The mechanism of the conversion process was quite similar to other studies on calcium silicates as reported previously.

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Three montmorillonites from Tsukinuno, Odo, Mikawa and one beidellite from Sano saturated with various cations (Li, Na, Rb, Cs, Mg, Ca, Sr, Ba, Ni, Co) were treated under hydrothermal conditions. Smectites changed to mica, chlorite and some non-sheet silicates through interstratified mineral phases. Three kinds of interstratified minerals were formed under the existence of cations as follows :1) rectorite : Na, Ca, Sr, Ba, (Li, Mg).2) tosudite : Li, Mg, Ni, Co.3) mica/smectite (random) : K, Rb, Cs. The formation temperature of interstratified minerals from beidelldte is lower than that from montmorillonite. The conversion temperature of interstratified minerals from momtmorillonite are different in each sample. Moreover, the Al-rich samples were more reactive and changed to interstratified mineral phases at lower temperature than the Al-poor ones. Thus, phases of interstratified minerals (particularly regular ones) are probably formed hydrothermally througf beidellitic compositions.

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Lithium-bearing donbassite and tosudite occur in veins in the Echassières granitic cupola (Massif Central, France). The two minerals are characterized by high Li contents and very low Fe and Mg contents; their structural formulae are :(Si_3.81Al_0.19)_4.00(Al_3.81Li_0.52Fe²⁺_0.01Ca_0.02Mg_0.01Mn_0.01)_4.38O₁₀(OH)₈(Na_0.07K_0.04)_0.11 for donbassite and(Si_3.50Al_0.50)_4.00(Al_2.95Li_0.22Fe³⁺_0.01Ti_0.01)_3.19O₁₀(OH)₅(Ca_0.01Na_0.15K_0.18)_0.34 for tosudite. Petrographic investigations of drill cores from the Echassières area indicate that these two minerals were formed in intermediate stages of a hydrothermal alteration series, muscovite-pyrophyllite-donbassite-tosudite-kaolinite, which occurred successively in the post-magmatic stage of granite. Fluid inclusion and stable isotope studies indicate that these aluminosilicates were formed at 400-150°C by interactions between low salinity (1-8 wt% NaCl) fluids of meteoric origin and the alkali granite.Thermodynamic calculations assured that Li-donbassite possessed the stability field from 300 to 200°C under acid conditions (3 < pH < 5) in the Echassieres hydrothermal system.

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Many thermodynamical interpretations are used in the study of weathering and hydrothermal alteration. In the simulation of the mechanism of alteration, it is necessary to introduce the factors of physical properties. We investigated the changes in the stability fields of several minerals in detail by the introduction of the parameter of pore size. (1) By assuming that the form of pore of rock or mineral is tubular, the pressure condition at the interface between solid and water change's as a function of diameter of the pore. (2) Water activity changes variedly by the given pressure and temperature. Water activity has been obtained as a function of diameter of pore in rock or mineral. (3) When the water activity changes, the stability field of each chemical species shift the phase boundaries (4) The values of thermochemical data, in particular Gibbs free energy of formation, differ with sources, so that the thermodynamical study on weathering and hydrothermal alteration needs the greatest care with respect to the change in water activity. These results are obtained for the system of K₂O-Al₂O₃-SiO₂-H₂O.

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Analysis of clay minerals by means of an analytical electron microscope have been reviewed from a standpoint of manufacturer. At present, two types of energy dispersive spectrometer are available for an electron microscope. The elements from Na to U can be detected by the Be window type detector and those from C to U, by the ultra thin window (UTW) type detector. Moreover, quantitative chemical analysis of thin section specimen can be made with a considerable accuracy by the Cliff-Lorimer method. Experimental factors such as, acceleration of voltage, dead time of detector, incident electron beam current, damage of specimen by an incident electron beam and contamination of specimen, should be given greater attention to get a more reliable result.

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Chemical compositions of kaolin group minerals, i.e. two kinds of dickite, three kinds of kaolinite and two kinds of halloysite, having various stacking orders and particle shapes, were examined by analytical transmission electron microscope (AEM). Analysed data using the spot mode in probe size of approximately 10 nm were apparently richer in SiO₂ than the ideal value of SiO₂ obtained by wet chemical analysis except for spheroidal halloysite. On the other hand, analysed chemical data by picture mode for 0.2μm×0.2μm region were in good agreement with ideal value, although those of disordered type kaolinite showed a little SiO₂ rich composition. The most probable interpretation for the difference observed between the spot mode and picture mode data was the channeling effect which occurs in the specific orientation between an incident electron beam and a crystal lattice. Furthermore, this effect results in the enhancement of an X-ray intensity for a specific element, although, probability due to the contamination and/or beam damage was also considered. Contents of Fe₂O₃ in kaolin minerals varied fairly widely among the specimens : Takabatake dickite (poorly ordered) < Red Mountain dickite (well ordered) < Oguni kaolinite (well ordered) < Georgia kaolinite (poorly ordered) < Indonesia halloysite (short tubular) < Motoyama Kibushi clay (disordered) < Ina hallysite (spheroidal).

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Chemical compositions of kaolinite, crocidolite, chlorite, sepiolite, chrysotile, beidelite and montmorillonite were analysed by analytical transmission electron microscope (AEM) and were compared with their bulk compositions measured by wet chemical method. Most of the data by AEM using approximately 10 nm probe size showed apparently richer in SiO₂ than those by wet chemical method. No significant influence by K-factors of water was recognized by the comparison of the data of kaolinite and metakaolinite, which was prepared by dehydration of kaolinite. Data by picture mode for approximately 0.2μm×0.2μm region for kaolinite showed in good agreement with ideal composition whereas data by spot mode analysed in the same region showed apparently SiO₂ rich composition, and were scattered very widely among particles. This anomaly in spot mode data was considered to be due to the channeling effect and possibly to the contamination and/or damage for the specimen by the incident electron beam.

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