Iôi ; S. SEKIYA AXD Y. KTKUCHI 



fore that which has often heen met with in other localities, the twinning plane 

 being Pöb . Parallel-intergrowth of the rhombic pyroxene with augite is , also 

 found. This has been dwelt on at length in the description of the Bonin specimens." 

 Though in specimens from Bandai this is not so clearly defined, yet we have found 

 some cases in which this phenomenon was very characteristically developed, the 

 crystal of the rhombic pyroxene being surrounded on both sides, or flanked on 

 one side, by an augite band. 



The rhombic pyroxene isolated from the rock by means of Thoulet's solution 

 and then lightly washed with hydrofluoric acid, was analyzed by Mr. T. Shimizu. 

 It was impossible to separate the rhombic pyroxene from the augite. The follow- 

 ing analysis is therefore that of a mixture. 



SiO, 51-80 ° , 



A1.,0 3 trace 



Fe 2 3 1-89 



FeO 18-8G 



Mn 3 0, 103 



CaO 7-0(1 



MffO 18-84 



100-88 



This leads to the composition nearly ecmivalent to 2 Fe SiO, + BMg Si (Vf- Ca 

 Si O,. 



Äfagnetite. — It is very abundant in grains, and as enclosures, especially in the 

 pyroxenes. 



Apatite— The crystals of this mineral sometimes occurs in a very character- 

 istic form. It is dichroic; || c = brownish, and J- c — yellowish. The crystals 

 usually with fine longitudinal striae, and with transversal cleavage -fissures. This 

 kind of apatite is very abundant in the lighter coloured rock which was found in 

 the bottom of the conical hole at Mine-yama. 



Tridymite. — This mineral is seldom found in the fissures in microscopic form. 

 In the rock imbedded within the hole at Mine-yama just referred to, it was found 

 in well-defined crystals visible to the naked eye, nearly -~)—l mm. in size, lining 

 the cavity of the rock in the manner of a druse. Some of them were found in 



* 1. c. p. 78. 



