156 



ART. 3. — B. KOTÔ : 



and Tertiary efïusives (PL XVI. Fig. 1) of southern Kyûshû than 

 the hlack historic volcanics of the island. The slaggy hollows in 

 the rock are often secondarily filled with calcite and primary 

 tridymite aggregate. It is a sHghtly slaggy, dopatic rock of light 

 color, in various shades of gray, wiiich entirely depend upon 

 different factors in the groundmass. The (a) brownish or purplish 

 tinge is due to hematitization through fumarole action upon augite- 

 needles and prismoids ; the {h) ash-gray tinge, which is very 

 common, is caused by slight admixture of the microlites of augite 

 and the crystals of magnetite in the plexus of feldspar microlites ; 

 the (c) wet-grey comes from flocky aggregation of augite-anhedrons 

 and magnetite dust ; and lastly, tlio {d) lightest shade and dull 

 lustre is attributable to the predominancy of feldspar microlites 

 and residual colorless glass. 



Phenocrysts of distinctly pleochroic pyroxenes, which are all 

 of brownish green, are scarce and only represented by slender 

 pleochroic hypersthene {h), 

 but those of (/) labra- 

 dorite (1-1.5 mm.) are 

 fairly abundant. Simple 

 anhedral feldspar, and 

 idiomorphic poly synthetic - 

 lamellar plagioclases as 

 well, are usually zonal- 

 structured. Glomeropor- 

 phyritic^^ {g) secretionary 

 patches of micronorite 

 (Text-fig. 32) play a part of 



phenOCryst, being COmpOsd Pig. SS—Micronontic segregation. 



1) Flocked together probably during the crawling of lava- streams. 



