岩石鉱物鉱床学会誌

The first occurrence of Judwigite in Japan is noted. The ludwigite occurs as an acicular crystal in forsterite aggregate from Hayama nickel mine, Fukushima Prefecture. In an extremely thin section, it has a strong pleochroism (Z'=dark brown, X'=green) and very high refractive indices. From a chemical analysis, given in Table III, it shows a good accordance with 4MgO•Fe₂O₃•B₂O₃, which has been generally accepted as the formula of ludwigite. When the X-ray powder pattern of the present mineral is compared with that of ludwigite from Hol-Kol, Korea, they show also complete agreement. From these data, the mineral is identified as ludwigite.

抄録全体を表示

抄録を表示する抄録を非表示にする

The crystals of augite were found in hypersthene augite andesite lava at Hontanigce of Aso-caldera, Kumamoto Prefecture. This area is composed of seven lavas of two-pyroxene andesite and its agglomerates, which are observed at the inside wall of somma. At Hontanigoe, a dyke is observed which strikes N70°E. This dyke is hornblende andesite and is very rich in large hornblende phenocrysts that often attain 1 or 2cm. in length.
The crystals of augite are greenish black in colour and idiomorphic with crystal faces a (100), b (010), m (110), and s (111), as shown Fig. I. The crystals of augite with shown a interpenetration twin have the following crystal faees; a (100), b (010), c (001), m (110), s (111), and p (101), as shown in Fig. 2.
This augite has the following opitical properties: α=I.686-I.689, β=I.692-I.694, γ=I.710-I.713, 2V (+) =57°-59°. Colour is yellowish green and its pleochroism is weak in thin section, X=pale green, Y=pale yellow, Z=yellowish pale green. The crystals of augite show the hcurglass texture and develop the zonal structure. Inclusions of augite are irregular magnetite and. idiomcrphic plagioclase (An. 57-62%).
The result of chemical analysis is shownin Table I. It is characteristic in its chemical constitution that this augite is rich in Al₃O₃ and poor in CaO. The writer presumes that this is related to the type of twinning and its opitical properties. The formula of the augite W. A. Deer & L. R. Wager follow: (XY)_1•970 ((Si, Al)₂O₆). The weight % as wollastonite (CaSiO₃), enstatite(MgSiO₃), and ferrosilite (FeSiO₃) are Wo: 39. 13%, En: 34.78%, Fs: 26.19%. In Table 2 is the constitutions as metasilicate.
In addition to, the Table 3 is the bulk chemical composition of the hypersthene augite andesite and the chemical composition of the hypersthene hyenccryst.

抄録全体を表示

PDF形式でダウンロード (418K)

J-STAGEへの登録はこちら（無料）