558 S. KOZU 



Olivine occurs in some specimens, as a very rare accessory in 

 an anhedral form. 



Magnetite is very scarce as phenocrysts. Minute euhedral to 

 anhedral crystals are disseminated in the groundmass, and form 

 about 4 per cent of the whole. It is also associated with the 

 aegirine-augite. 



Apatite is conspicuous as very minute needle-shaped crystals. 



Chemical characters. — Separate analyses were made of the rock 

 and of the porphyritic anorthoclase. 



For the purpose of analysis of the mineral, the phenocrysts 

 were picked out of the weathered rock, in which the minerals remain 

 on the surface in a favorable state to be taken off from the matrix. 

 The feldspar material is quite fresh, but the surface and the inner 

 portions along the parting and cracks are stained by decomposed 

 products from the matrix and inclusions. To purify it as much as 

 possible, it was crushed into 1-2 mm. grains and was digested in 

 dilute hydrochloric acid at 8o° C. for 24 hours, until it turned 

 white in appearance. But an intimate association with impurities 

 rendered it impossible to prepare a thoroughly clean sample, so 

 that the results of analysis are somewhat unsatisfactory. The 

 chemical analysis, made by S. Kawamura in the laboratory of 

 the Imperial Geological Survey of Japan, is as follows: 



Si0 2 64.98 



A1 2 3 19.62 



FeA 0.98 



MgO o. 22 



CaO 3-48 



Na 2 4-86 



K 2 583 



99-93 

 By the withdrawal of the excess of silica, lime, magnesia, and 

 iron as impurities mainly due to inclusions, the chemical composi- 

 tion of the mineral is shown approximately by the following ratios: 



Si0 2 63.08 



A1 2 3 21.80 



CaO 3-24 



Na 2 5-39 



K 2 6.49 



