Problems in measurements of surface area and pore size distribution are discribed. On the specific surface area, BET method and Blaine's method are comqared. On the measurement of pore size disstribution, differences among BJH method, Cranston-Inkley method and Model-less method, and comparison between gas adsorption method and mercury intrusion porosimetry are discussed. Pore structure of hardened cement pastes is mentioned, as an example, concerning with their properties.

View full abstract

In the course of field survey in Shigiyama area near Yawatahama, Ehime Prefecture, it was found that a clayey material with leather-like appearance occurred as a filling of fissures developed in a serpentinite. The “leather” was about 1 cm thick and grayish green or colourless, and exhibited fibrous texture. X-ray, thermal (DTA, TG, DTG), infrared, and electron optical analyses of the bulk sample and <2μm size fraction separated have shown that the “leather” consisted principally of well-crystallized sepiolite (“α-sepiolite”) with some calcite as an impurity. Elemental analysis of the<2 fpm size fraction indicated Si and Mg as principal cations, and this result together with X-ray and thermal data fitted the Brauner-Preisinger model rather than the Nagy-Bradley one, giving a structural formula:(Mg_7·63 Mn_0·02 Fe_0·28Al_0·06) Si_11·99O₃₀(OH)₄ (OH₂) ₄·9.12H₂O
Minerals of MgO-SiO₂-H₂O system such as well-and poorly-crystallized serpentine, hydrated talc and stevensite have been formed, along with aragonite, as hydrothermal products witin the serpentinite. Such mineral association and published data of hydrothermal phase transition for sepiolite suggested that the sepiolite has been crystallized from low-temperature Mg soultion at the latest stage of hydrothermal process, according to the sequence, serpentine (chrysotile)→poorly-crystallized serpentine+hydrated talc→hydrated talc→stevensite→sepiolite.

View full abstract

In this study, the shapes of tubular halloysite crystals formed in granitic and rhyolitic rocks by weathering and hydrothermal activities were observed in detail under the transmission electron microscope.
Halloysite specimens of weathering origin were collected from remarkably altered parts surrounding core stone and altered granitic and rhyolitic gravels in sediments. The hydrothermal halloysite specimens were collected from hydrothermal clay deposits in granitic and rhyolitic rocks.
The difference of shapes (the width and length of crystals) of tubular halloysite was paied special attention. The mean value of width and length of tubular halloysite crystals in a specimen was measured, and slso the value of its standard deviations was caluculated. The result shows that the width of halloysite crystal is clearly different between hydrothermal and weathering products, though the difference of its length is not recognized between both genesis. The mean values of width and its satndard deviatian of hydrothermal halloysite are distinctly smaller than them in weathering products.
This result indicats that it is possible to distinctly know the genesis of tubular halloysite formed in altered granitic and rhyolitic rocks based on the mean value of width of halloysite crystals.

View full abstract

Recent progress of X-ray powder pattern analysis is reviwed on (1) identification, (2) indexing, (3) pattern fitting structure refinement and (4) factorial analysis. In the identification and indexing problems. many applicable methods are reviewed. Emphasis has been placed to the accurate determination of individual peak positions to obtain successful results. In the pattern fitting structure refinement, a method develpoed by Young et al. is introduced with an application example for muscovite structure. In the factor analysis, a new technique to estimate the effects of experimental factors using many X-ray powder patterns is introduced with an application example for the formation of CaCO₃ polymorphs.

View full abstract