274 K. jiMBo : 



of two crystals, which are in themselves polysynthetic twins, either 

 of the Albite or Pericline type, or of both at the same time. 

 The rectangular crystal, as well as one half of the cross-shaped 

 or broad-tabular twin, is apparently simple, but really shows 

 grooves of the Pericline twinning and striations of the Albite 

 twin. The presence of Manebach twins is doubtful ; apparently 

 complex crystals composed of many prismatic forms as in a 

 cross-shaped twin, are nothing but irregular groups. 



120. Labradorite. 



Wada possesses a piece of grey labradorite from Mineoka 

 in Awa,* (Honshu) ; this specimen labradorizes distinctly in con- 

 trast to the plagioclase forming a constituent of the gabbro of 

 this place. 



121. Anorthite. 



Kikuchi (Journal of the Science College of the Imperial 

 University of Tokyo, 1889) has given a detailed description of 

 separate anorthite crystals of Miyakejima. They are perfectly 

 developed on all sides and covered with a black coating of lava. 

 Their form is thick tabular, either apparently simple or in 

 Carlsbad twins. The longest diameter of the crystals is about 

 2 cm. Observed crystal faces are oP, coPoo, <xT, co P'^ co'Pï, 



œF3, ,P,^, 2'F^, ,,P^^, ^P'^, 2'Pœ, F, ,P, P„ 4'Pï, 4P,T, 



4,P2' and 2P, (?), among which oP, a)Pœ, 2,P, c^, 2Tœ, and 

 2P' 00 are most frequently found. Kikuchi has mentioned be- 

 sides analysis by Kitamura, various artifical etching figures, prin- 

 cipal optical characters, &c. 



The same author found a similar anorthite in a volcanic 

 rock of TÖNOSAWA in the old volcano of Hakone. 



