262 K. jiMBü : 



e.) Purplish-white mica (rare), with a large optical angle 

 and the optical plane parallel to the symmetry plane. 



Fnkuchi has found, that the muscovite (b) shows a transition 

 into the dark-green biotite, either directly or through inter- 

 mediate stage of alteration represented by the zinnwaldite (a). 

 The biotite is surrounded sometimes by the zinnwaldite and 

 sometimes by the muscovite, their boundaries against the en- 

 closed biotite being often very distinct. 



Odayama near Mt. Tsukuba in Hitachi. — In the granite of 

 this place are found small plates of white mica with a brownish 

 grey tinge. It resembles the zinnwaldite of Tanokamiyama. 



Various mica specimens of white, brown, green, and other 

 colours are found at several other localities in Japan. A dirty 

 dark-brown mica of Ivai has been known from early times, by 

 its elongating into a long columnar form, when put on charcoal 

 fire. Its analysis by Hida is as follows : 



100.10 



101. Ottrelite. 



This mineral was found in microscopic individuals in a 

 slide of the hornfels from the Hidaka mountain-range in Hok^ 



