Vivianite nodules 1-8cm. in diameter, some of them taking the shape of tree-trunk or mammal bone, have been found in gravels and mudstone bed at the beach Subana in the Island of Himeshima, Ooita Prefecture, Japan. They are composed of radial aggregates of foliated vivianite crystals. The specimens collected from the gravels are covered with brown film of limonite. The observation on the fresh vivianite from Himeshima follows; colour: yellowish or deep blue, streak: blue, hardness: 1.5-2, sp. gr.: 2.66 at 17°C., cleavage: (010) easy, luster: vitreous, indices of refraction: α=1.587, β=1.607 and γ=1.631, 2V large, pleochroism: X blue, Y colourless or yellowish and Z yellowish, optical orientations: X//b, Z∧c about 27°. Small but good crystals of vivianite are found on the wall of druses. They have short prismatic habit with monoclinic symmetry. Forms: b (010), m (110), w ( ?? 01), T (103), d (801), x (221) and V (441). The result of chemical analysis of a nodular specimen follows, P₂O₅ 24.43, Al₂O₃ 2.49, Fe₂O₃ 6.84, FeO 30.04, MnO 0.24, MgO 0.28, CaO 0.06, Na₂O tr., K₂O tr., TiO₂ tr., SiO₂ non., SO₃ non., insol. 10.36, H₂O (+) 13.05, H₂O (-) 12.65, total 100.44%, and that of a specimen in tree trunk shape follows, P₂O₅ 26.84, Al₂O₃ 0.59, Fe₂O₃ 14.00, FeO 29.30, MnO tr., MgO 0.10, CaO 0.12, SiO₂ 0.42, insol. 0.06, H₂O (+) 16.11, H₂O (-) 12.35, total 99.89%. In the nodular sample, some clay inclusions are observed under the microscope. The main features of X-ray powder diagram of the tree-trunk-shaped specimen agrees with that of the well crystallized vivianite from the Ashio mine, Tochigi Prefecture, Japan.

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Phenomenological equations for the refractive indices of orthopyroxenes are derived as a function of concentrations of constituent cations. Coefficients in these equations represent the coherent effects of individual cations on the refractive indices. The refractive indices calculated from the resulting equations are in rather good agreement with those observed. Thus probable changes in the refractive indices of the orthopyroxenes with ion substitutions are examined, in comparison with those of the clinopyroxenes.

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The optical properties and unit cell dimensions of cordierite were studied for the purpose of presenting methods for the estimation of the (Fe⁺²+Mn):(Mg+Fe⁺²+Mn) ratio and the degree of distortion (deviation from the hexagonal indialite structure) of the minerals. The results are summarized in determination diagrams given in this paper. The unit cell dimensions of indialite were compared with those of cordierites and the relation was established that the unit cell volume of cordierite increases with the increase in the degree of distortion. The study also revealed that the optical properties of volcanic cordierite differ considerably from those of high cordierites inverted from low subdistortional cordierites by heating and the cause of this difference is discussed.

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