ox THE yO-CALLED CKYSTALLLNE «CHIöTÖ OF CHICHIBU. 105 



Calotte with its ch'iracteristic rhoiiibohedral cleavage filJs up the 

 miarolitic spaces. It is, however, not a constant component. Iron- 

 pyrites and iron-glance are tolerably ])lcntifn], the latter with margins 

 of blood-red iron-mica. Quartz and rutile, so abundantly present in 

 the Lower Sambagawan series, are only of a subordinate importance. 



We occasionally met with tilanite as an enclosure in felspar in 

 combination with the clinodome (n^xPco). and prism ( / ^=Px ) 

 as in fuj. 12. a VI. 11 ; consequently its section in a slide mostly 

 presents a rhombic outline with a deeper shade on the two adjoining 

 sides (^fig. 12. h) which make with each (jther an obtuse angle of 

 13J:°-137^. This difference in shade arises necessarily from the very 

 form of the crystal itself, and is due to the inclination of the clinodome 

 or prism. Thus the habitus of the microscopic crystal differs from 

 the macroscopic type, as has already been pointed out by y. Foullon.i^' 



The structural modification of the rock is still more astonishing, 

 ranging from a coarse-lamellar rock to an almost compact schist. 

 A newly fractured surface of the former variety shows felspar-spots 

 of a tolerably large size (more than '1 mm.) with a glittering ])lane of 

 cleavage. In the compact variety, it differs in no wise from a common 

 chlorite-schist. The weathered surface, however, distinctlv tells the 

 presence of countless white spots of felspar-grains. 



The compact variety is somewhat more yellowish-green in 

 colour on account of the presence of a considerable quantity of epidote 

 as in the rock of Oda, 1 7« ri (6 km.) westward from the small town of 

 Kodama. There also numerous clusters of black tourmaline-cvys>Xu\îi, 

 attaining the size of 1 centim. in length, are found along the plane of 

 stratification of the rock. Slides show that the mineral has a grayish- 

 brown colour wdtli a slight tinge of violet ; zonal structure is more 



1) Heinrich Baron v. Foullon ; Ueber die petrographischc Bcscliaffeuheit der Krystalli- 

 nischen Schieferj etc. Jahrbuch d. geol. Reichsanstalt, 1883, p. 241. 



