Vulc.mo Obhima, Idzu. ^J 



belong to the {Xirfelic order with either a neghgible amount of 

 quartz or none, while those belonging to the quardofelic order are 

 not yet known to have such calcic plagioclase as bytownite.'^ 

 Thus, the rock now under consideration is quite unique in its 

 composition. 



Of the quardofelic aphanites characterized by lime-soda-feld- 

 &pars, those with normative oligoclase, andesine, and labradorite are 

 respectively called ungaite, shastaite, and bandaite. It is clear from 

 the characters described above that the present rock must occupy 

 the vacant position next to bandaite, or thereabout in the same 

 group, being characterized by normative bytownite. Thus, it seems 

 to be necessary, on account of its peculiar characters, to give a 

 new name to our rock, for which " miharaite "'^ is here proposed, 

 derived from the name of the central cone, Miharayama.''^ 



In the following table, miharaite is compared with (i) the type- 

 basalt given by Robinson,'^ (ii) the alboranite from Isla de la Nube, 

 Alboran, described by BECKE^^ and (iii) the diabase from Barima 

 District, British Guiana, described by Haekison.^^ 



A Average composition of the present rock 'HI. 4'. 4'. 4. 



B Type-basalt, calculated by Kobinson from 246 analyses in II. 



5. 4. 3., in. 4. 3. 4., in. 5. 3. 4 & 5., III. 5. 4. 3., III. 5. 5. 



C Alboranite, 'III. 5. '4. 3(4). auvergnose. 



D Diabase, 'HI. '5. '5. 5. ouenose. 



1) Iddings says, in a description of the pbanerites belonging to the same group as the 

 present rocb, that the feldspars of any rock of this group almost never average as calcic as 

 bytownite-anorthite (Igneous lïocks. Vol. II., p. 4i, 1913). 



2) " Mihara-g.an " (Hj^ë") i^ Japanese. 



3) =^04 



4) " The San Franciscan Volcanic Field, Arizona," U. S. Geol. Surx:, Prof. Paper No. 76, p. 

 101, 1913. 



5) Tschermak's Min. u. Petr. Mitth., Ed. XVIII., S. 520, 1899. 



6) Hep. G. K W. Dislrirt, II., p. 6, 1898. Keproduced in the following works: — 



H. S. Washington, " Chemical Analyses of Igneous Kocks," V. S. Geol. Sun:, Prof. 

 Paper No. 14, p. 337, 1903. 



Iddixgs, Igneo%is Hockg, Vol. II., p. 227, 1913. 



