The boundary between normal and abnormal interference colour was discussed from the view point of colorimetrics. The ellipses ten times as large as the MACADAM'S ones were adopted as the discriminating limit of colour to determine the boundary. The results of calculations showed that the abnormal interference colour series does not uniformly approach one in the normal series throughout the whole colour arrangement.

抄録全体を表示

Phase changes of carpholite during heating have been studied by X-ray powder method, along with differential thermal and weight loss analyses. The results are shown schematically as follows:
It has been observed that tridymite is formed as an intermediate phase during the transformation from quartz to cristobalite.

抄録全体を表示

Recent experimental works have shown that clinopyroxene of MgSiO₃-FeSiO₃ series has a stability field at high pressures and at temperatures lower than several hundred degrees. But review of the data on natural pyroxenes suggests that pigeonite crystallizes from magmas within its own stability field at temperatures higher than that of orthopyroxene stability. There are also some experimental evidences in favor of the existence of a form of clinopyroxene stable at high temperatures. Crystallization of orthopyroxene and pigeonite from basalt magmas is discussed on the basis of hypothetical phase diagrams of MgSiO₃-FeSiO₃ system and also of (Mg, Fe) SiO₃-Ca (Mg, Fe) Si₂O₆ system. No drastic change is needed for the existing theories on the crystallization of pyroxenes from magmas. It is pointed out that an existence of the stability field of Mg-Fe clinopyroxene at low pressures and low temperatures raises many serious questions which are difficult to answer.

抄録全体を表示

Details of the oriented transformation of johannsenite to bustamite, have been studied by the single crystal X-ray method, in order to elucidate the transformation mechanism for silicate chain structures in general. A single crystal of johannsenite was heated at 900°C in a silica tube. The product is a pseudomorph in which the johannsenite has been partly changed into bustamite. The latter is formed in a definite orientation relative to the johannsenite: the sheet of closed-packed oxygen atoms of johannsenite makes an angle of 4.5° with that of bustamite and [012] of johannsenite coincides with [11^-1] of bustamite. This orientation shows that a dense zone of large cations and silicon atoms in johannsenite is preserved in the transformation.
These results are interpreted on the basis of the preservation of the close-packed framework of oxygen atoms along a dense zone of metal cations and silicon atoms in johannsenite in the transformation. The differences in the direction of the SiO₃ chains and in the ordering of Ca and Mn atoms in the johannsenite and bustamite structures provide direct evidence of the migration of Ca and Mn atoms as well as of Si atoms during the transformation.
The oriented transformation of rhodonite to wollastonite, described by DENT GLASSER and GLASSER, is better explained by the same principle as the johannsenite-bustamite transition than by that of simple preservation of the close-packed framework of oxygen atoms.

抄録全体を表示