20 "V'ol- XLIII., Art. 5.— T. Kalo: 



double-refracting minerals now admixed with the groundmass. In 

 the groundmass, a small quantity of biotite occurs in irregular 

 microscopic flakes sometimes overlapping the microlites of feldspar 

 and pyroxene. It is characterized by strong pleochroism, perfect 

 cleavage and a nearly uniaxial interference figure under th& 

 conoscope. 



As phenocrysts occur plagioclase, hornblende and hypersthene. 

 The plagioclase occurs in tabular idiomorphic crystals often attaining 

 a length of 3 mm. It shows broad polysynthetic twin-lamellae^ 

 From indices of refraction and extinction angles, it is identified a& 

 labradorito. The hornblende is variable in amount and size even 

 in different portions of the same dyke. It ranges from a micro- 

 scopic size to several millimeters in length, and commonly occurs 

 in well-defined crystals, showing distinct pleochroism, brown to 

 light brown, and small extinction angle, c : c=20°. The hypersthene 

 occurs in well-defined prismatic crystals characterized by the 

 prismatic cleavage, transverse cracks and straight extinction, and 

 shows distinct pleochroism, H c pale green and ± c light brownish 

 yellow. 



T 100- Pyroxene Andésite, This occurs in small dykes, with a 

 thickness varying from a fraction of a meter to 1 meter or more, 

 in the Daisen area. One of this type is found near the entrance 

 of the Kisei main adit, the southern continuation of the Daisen 

 adit, striking N.-S., while another one is found a few hundred 

 meters distant from the same entrance, running N. W. to S. E. 

 obliquely across tlie Daisen vein (PI. L). 



The rock is much decomposed and show^s an earthy, compact 

 texture with a light grayish colour. Abundant phenocrysts of 

 feldspar with a length up to 1 mm. are visible. Long prismatic 



