On Anorthite from Miyakejima, 



hV 



Yasushi Kikuchi. 



Assistant Profossni- of Geology, Imperial University. 



With Plate I. 



The AnorHiite-crv.stuls which form tlie subject of the ]»re8eijt 

 cominnniciition were collected l)y Messrs, S. Okiil)o and X. <Jkada of 

 the Iinnerinl University (m the Island of Mivake. forniino" one of the 

 Shichiîô or Seven Islands Group, situated to the soutli ofthelzu 

 iDeninsuln. Mv best thanks are due to those o'entlenien for kindlv 



± */ CD %f 



placing the specimens at my disposal. 



The Shichiîô Group is part (^f a chain of volcanoes of which 

 Fuiivama is the hio;liest, h:ivin2r its orioin in Central Ja])an.and stretch- 

 ing in a SSE direction toward the Ladrone Islands in the North 

 Pacific. The volcano on the Island of ]\Iivake is kn(^wn to have 

 erupted occasionally within ]nstori<'al times. The last of tliese erup- 

 tions took place in the 3rd «^f July 1874 (7th year of Meiji) and de- 

 stroyed by a lava-flow, a place called Tö^ö in the villaoe of Kamitsuki. 



The Anorthite-crystals here descrilied are fourid forming- a 

 primary constituent (^f a basaltic lava. It is iKuvever remarkable, 

 that these crystals, besides entering into the por[)liyritic constituerit 

 of the lava, are f(mnd scattered on the lava-field formed by the erup- 

 tion just mentioned, as well-defined separate crystals, in a luanner 

 which admits of no doubt as to their having been thrown c>ut of the 

 crater as such.* A. Penckt has indicated the pi)ssibility of such 



* During a recent visit to Siilplmr Islau^l, I have obssrvetl the same phenomenon. Felspar 

 crystals, the nature of which awaits further investigation, are fauml, covered with a black hxva- 

 crast, and forming a loose superficial layer in the vicinity of a volcano on that Isliud. 



t Studien über lockere vulkanische Auswürfiiuge— Zeitschft. d. deutsch, geol, üesellft. Bd. 30 

 1874. p. 124. 



