Mineralogical descriptions are made for the Taishu hakudo and Taishu toseki which have been mined as refractory clay and a raw material for sanitary ware at Azu in the Tsushima Shimoshima Island, Nagasaki Prefecture, Japan. These ores were formed by hydrothermal alteration of quartz porphyry of Miocene age. X-ray powder diffraction, electron probe microanalysis and polarizing microscopy have revealed that the Taishu hakudo (white clay) is composed mainly of halloysite and the Taishu toseki (altered quartz porphyry) is composed of 2M₁ sericite, Ca-beidellite, albite, quartz, etc. with residual quartz and oligoclase.
The toseki is well jointed in the same direction with a vertical dip, and the alteration products are abundant along the fissures. Three types of alteration can be recognized at this deposit. The first alteration is characterized by the assemblage of albite, sericite and beidellite which crystallized in this order. This alteration is considered to have transformed quartz porphyry into toseki by pervasive alteration around the fissures subsequent to the igneous activity of the original quartz porphyry. The second alteration is characterized by the assemblage of FeMg-chlorite, sericite, calcite and galena and the assemblage of interstratified chlorite/vermiculite, sericite and quartz which were formed filling the fissures and disseminated in the toseki. The hydrothermal solution of this alteration may have a genetical relation to a granitic pluton near this deposit. The last alteration is intense halloysitization which affected the toseki pervasively around the fissures and formed the hakudo.

View full abstract

Properties of a clay floc such as volume, structure, density, and strength are important factors to analyze the flow behavior of a flocculated clay suspension, since the dispersed clay floc (enclosed water) can be considered to behave as a flow unit during flow. In this study, the effective volume fraction of kaolinite floc during flow was examined by comparing a viscosity equation involving the effective volume fraction of floc as a parameter and the measured values of viscosity of flocculated kaolinite suspension. The viscosity of this suspension was measured using a vibro viscometer as functions of solid volume fraction and NaCl concentration. It was found that the effective volume fraction of kaolinite floc was about ten times that of kaolinite particles and this fraction increased with increasing of NaCl concentration.

View full abstract

Zeta (ζ) potentials of the clays saturated with various ion species estimated by electrokinetic sonic amplitude (ESA) method reflected the corresponding mean particle or aggregate size which showed the dispersibility, as generally mentioned.
In kaolin minerals such as kaolinite and halloysite, the value of ζ-potential and the dispersibility were affected with the difference of cationic valence, but they were not concerned with the cationic or hydrated ionic radius. The neutralization of surface charges on clay particles by monovalent cations was hardly perfect in kaolin minerals. On the other hand, divalent cations were perfectly neutralized the surface charge, and ζ-potentials of kaolin minerals saturated with them showed about zero.
In montmorillonite, Li⁺ and Na⁺ were adsorbed in its interlayer poison as hydrated ion, its surface charges on particles did not neutralize perfectly, and made the ζ-potential relatively high. The dispersibilities of Li⁺-and Nat⁺-saturated montmorillonite were extremely high, in consequence. Rb⁺ and Cs⁺ were, however, adsorbed strongly in the interlayer position of montmorillonite as nonhydrated ion, and they negated perfectly its surface charges. On the other hand, divalent cations neutralized perfectly the surface charges of montmorillonite although they were adsorbed as the hydrated form in its interlayer position. The ζ-potentials of Rb⁺-, Cs⁺-, Ca²⁺-, Sr²⁺-and Ba²⁺-montmorillonite were nearly zero, and their dispersibilities were also low.
In allophane, the value of ζ-potential and the dispersibility were affected with the difference of cationic valence, but they were not concerned with the cationic or hydrated ionic radius. The negative charge of allophane was not perfectly neutralized by monovalent cations, but it was perfectly done by divalent cations, in higher pH region than its isoelectric point. The neutralization of positive charge of allophane by monovalent anions was hardly perfect in the pH region below its isoelectric point. On the other hand, divalent anion was perfectly neutralized the positive charge of allophane, and its ζ-potential saturated with SO₄^2- was shown zero, and its dispersibility also relatively decreased.
It is concluded that the estimation of ζ-potential by ESA method in clay minerals saturated with various ion species was effective, and gave a similar result of the previous studies by applying other methods such as electrophoresis and ultrasonic vibration potential.

View full abstract