Celadonite, a green coloured mica clay mineral, is found in amygdales of altered dolerite at Taiheizan, Akita Prefcture. The specimen gives basal reflections at about 10Å and its submultiples, and its crystal structure is identified as a 1M polymorph from powder diffraction data. Although a DTA curve shows a small endothermic peak at about 100°C, the 10Å reflection was not affected either by heat treatment or by saturation with organic liquids. An infra-red spectrum is similar to that of a ferric celadonite reported by Farmer and Russell (1963). Chemical composition: Si0₂ 50.84%; TiO₂ trace; Al₂O₃ 5.08; Fe₂O₃ 19.35%; FeO 2.28%; MnO trace; MgO 6.10%; CaO trace; Na₂O 1.24%; K₂O 8.75%; H₂O⁺ 4.48 96; H₂O^-0.85%; total 98.97%.

View full abstract

The electron spin resonance (ESR) spectra of two samples of allophane suggested that ferric ion substituted partly for aluminum ion in its structure, and that the ferric ion was located in a poorly crystalline environment. Allophane may not be perfectly amorphous, but of poorly crystalline form.

View full abstract

Unusual accumulation of yellowish gray clay materials has been noticed at places in the lower part of the Kitakami pumice bed. Field survey and laboratory examinations have revealed that this accumulation is mainly a secondary deposition of the clays carried down by percolating water. The deposition was apparently accelerated by water stagnation caused by an underlying Pleistocene clay bed as a slowly permeable layer. Gibbsite, halloysite, and allophane were the dominant clay minerals in the accumulated material with some imogolite and free sesquioxides as accessory constituents. The sum of the content of the former two minerals amounted to 35 to 40 per cent, and was higher than that in the clay fraction of the upper part of the pumice layer where no accumulation occurred. The relative concentration of gibbsite and halloysite was accounted for by their high dispersibility relative to allophane in the percolating water. Chemical analyses have shown that a considerable amount of Al together with Si is liberated rather continually from the upper pumice bed. The concentration of Al in water extracts of a moist sample taken from the field was evidently higher than that expected from its solubility in the same pH range probably owing to the presence of organic matter, but decreased to a few-hundredths upon mild air-drying of the sample. These results suggested strongly that aluminum hydroxides and silica-alumina coprecipitates form rather readily, and evolve to gibbsite, halloysite, imogolite, or possibly allophane in the pumice bed.

View full abstract

The heat of immersion of allophane and imogolite with a number of organic liquids was measured in order to investigate their interaction. The same measurement was carried out for layer-silicate clay minerals as reference.
The heat-of-immersion values decreased in the order: methyl alcohol>ethyl alcohol>n-propyl to n-decyl alcohols. This order was common to both allophane and layer-silicate clay minerals. The higher values for methyl and ethyl alcohols were ascribed to their greater energy and amount of adsorption. These two alcohols were considered to be adsorbed mainly by the hydrogen bond, whereas the alcohols containing more than three carbon atoms by the van der Waals force. The heatof-immersion values for allophane were higher than those for layer-silicate clay minerals, suggesting that the former has larger number of surface OH groups than have the latter. The difference in the heat-of-immersion values between ethyl alcohol and ethylene glycol was interpreted in terms of the difference in their energy of adsorption due to the difference in their polarity. The differences were also found in the heatof-immersion values for the isomers of butyl alcohol, probably reflecting the effect of the shape of molecules on their adsorption.
There was no noticeable difference between the heat-of-immersion values of allophane for polar and nonpolar aromatic liquids. From this were inferred the similarity in the amount and energy of adsorption of both the groups of aromatic compounds, and the van der Waals interaction between them and allophane. The heat-of-immersion values for montmorillonite were notably higher with a polar aromatic liquid than with a nonpolar one. The heat-of-immersion values for nonpolar liquids decreased from benzene to n-hexane through carbon tetrachloride. The heat-of-immersion values in nonpolar liquids were remarkably higher for allophane and imogolite than for montmorillonite. This difference was correlated with the difference in their surface area, determined by N₂ gas adsorption.

View full abstract

A clayey material consisting predominantly of the trioctahedral 2: 1 phyllosilicate which is similar to talc rather than stevensite, with a basal spacing of 9.7 A, was found in hydrothermal-alteration products of wollastonite-rich skarn at the Akatani copper-iron mine, Niigata Prefecture, Japan, by one of the present authors (N. I.). The material occurs as a small pocket in the wollastonite-rich skarn, and is pseudomorphous after wollastonite. Field relations indicated that the small pocket is located in an intermediate subzone between inner talc and outer stevensite zones.
Chemical analysis of the clay fraction less than 2μ leads to the following structural formula for the mineral in question per unit-cell-layer on the basis of O₂₀ (OH) ₄ anion unit;
(Mg5.81 Mn²⁺_0.40 Fe³⁺_0.06)(Si_7.73 Al_0.15) O₂₀ (OH) ₄ (Na_0.02 K_0.02)-EnH₂O.
X-ray diffraction, thermal and infrared absorption analyses revealed that the mineral in question is a variety less hydrated than stevensite, and may be named as “hydrated talc”.
Based upon the field relations, information on the formation temperatures of minerals from the mine obtained by means of fluid-inclusion thermometry, and the synthetic data for the system MgO-SiO₂-H₂O, the mineral in question was identified as an alteration product of the preexisting wollastonite at temperatures of 250°-300° by the action of magnesium-bearing hot water, which journeyed through a channel-way immediately before ore-formation and simultaneously dolomitized limestone wallrock.

View full abstract