﻿ASBESTOS AND MANGANESE DEPOSITS. 157 



scrap mica finds commercial use for boiler and pipe lagging, for roofing 

 and fireproofing materials, as a lubricant and for decorative work, wall 

 papers and paints. If any small sheets should be found they could be 

 worked up into "micanite," now extensively employed in insulating 

 certain parts of dynamos. 



Extensive development of mica schists occur in this region, paragonite 

 and margarite being the predominant micas. 



Scales of this white mica, when viewed in a petrographic microscope, 

 show a fine interference figure with an axial angle of 37°. A qualitative 

 analysis demonstrates the presence of sodium and calcium, so that we 

 probably have both paragonite, the sodium variety, and margarite, the 

 calcium mica. 



Magnetite schist. — Many outcrops of schists occur in the vicinity of 

 the Baruyen Eiver and magnetite schist, in which the magnetite cubes 

 and octahedra attain a diameter of 10 millimeters or more, is found 

 among these. 



Epidote-magnetite schist. — This rock, in thin section, consists largely 

 of a felty mass of actinolite and chlorite with phenocrysts of magnetite 

 and epidote. The magnetite occurs in diamond and octagonal sections, 

 also is rounded and irregular grains; the epidote, in idiomorphic crystal 

 sections is on the average 0.67 by 0.08 millimeter. These epidotes are 

 distinguished by high relief, parallel extinction and the characteristic, 

 irregular fracture. The difference in absorpton along the a and b axes 

 is as follows : a=colorless, b=straw yellow. 



Conclusions in regard to the schists. — It is quite possible that some 

 of these schists may be metamorphosed ancient sediments, although this 

 is not very probable. The presumption is that they are of very recent 

 origin. We doubtless have as much reason for placing them in the 

 Archean as have some writers in the case of the crystalline schists of 

 Formosa, but there is absolutely no paleontologic evidence in either 

 case. 



THE SEDIMENTAEY FORMATIONS. 



The following sedimentary formations are found in this region, flank- 

 ing the basal core of the rocks and in some places as residual patches, in 

 tiers, resting upon the older formations : 



The order is from above downward, and only tentative, as contacts or sections 

 including more than one formation are very infrequent. 

 Raised coral reefs. 

 Marl beds. 



Orbitoidal limestone. 

 Ash beds with sandy shales alternating. 

 Calcareous sandstone. 



Coarse grained sandstone and shale beds alternating. 

 Ferruginous cherts and slates, jasper. 



"Outlines of the Geology of Japan, Tokyo (1902), 26, 33. 



