634 s - K0ZU 



megascopic phenocrysts of feldspar and pyroxene, their sizes vary- 

 ing from i mm. to 2 mm. The other specimens taken from the 

 new dome are dark gray, or reddish dark gray, in color and spongy 

 or ragged in appearance. Generally, they are characterized by 

 heterogeneity in texture due to their variable crystallinity, and by 

 flow-structure, which is visible in the lava-mass, as shown in Fig. 3. 



Fig. 3. — Lava-block, showing the marked flow-structure 



Sometimes dark-gray to light-gray cryptocrystalline masses are 

 imbedded along the planes of flow in the rock-mass, their shapes 

 being mostly lenticular. 



Microscopical characters. — -The rock is made up of plagioclase, 

 hypersthene, augite, olivine, magnetite, apatite, and microliths, 

 scattered in the abundant glassy groundmass. The prevailing 

 phenocrysts are of anorthite. Hypersthene comes next, and is 

 nearly equal to, or is more than, the augite. Subhedral magnetite 

 is not rare as phenocrysts. Though olivine appears abundantly 

 associated with the large crystals of anorthite, mostly as peripheral 



