Twelve chrysotile samples with different degree of softness were selected from main chrysotile deposits of the world, and the correlation between the softness of chrysotile asbestos fiber and few other properties of them, namely crystallographic characteristics of individual fiber, morphology of fiber bundle and impurities contained, were studied.
It was revealed that the difference of softness depends on the degree of bonding strength between individual fiber and not on the polymorphic forms or degree of crystallinity of chrysotile.
Various kinds of impurities were contained in chrysotiles used in industrial purpose, and it could be pointed out that harsh chrysotile asbestos fiber contain mainly magnesium silicates such as antigorite and talc os impurities.

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A radomly interstratified mineral (mica-montmorillonite) with cation-exchangeable property was found in the Mine of Ebara, near Kinosaki, Hyodo Prefecture.
Its basal spacing is 13.7Å, 12.6Å and 11.6Å in each humid, ordinary and dried air condition respectively.
The mineral changes to regular interstratified mineral (chlorite-montmorillonite) with 30Å spacing at I kb water pressure in the range from 360°C to 480°C. At temperatures over 480°C, it changes to a mica mineral.
When the starting material is used after treating with hydrochloric acid, it direcly changes to mica at 380°C and 1kb.

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The study on the thermal transformation of illite was made by differential thermal analysis, thermo-gravimetric analysis and X-ray powder diffraction, and the transformation mechanism was discussed from structural point of view. The process of thermal transformation of illite can be summarized as follows:
Illite500°C Illite anhydroxylate 900°C Spinel-type oxide 1050°C Fe-bearing spinel
1100°C Mullite.
Futhermore, above about 850°C and immediately following the destruction of the dehydroxylated phase, a glass phase appears, and hematite starts to from at about the same temperature and melted into a glass phase above 1200°C.
An investigation of the transformation mechanism was made using an oriented specimen of illite. The following topotactic relations among the original illite and high temperature phases were maintained through the entire transformation process:
(001)I//(001)I·A//(111) Sp//(c-axis)M,
where the suffixes I, I. A, Sp and M signify illite, illite anhydroxylate, spinel-type oxide and mullite, respectively. The thermal transformation process of illite is characterized by a structural continuity reflected by the topotactic transformation mentioned above.

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