ON THE SO-CALLED GEYSTALLINE SCHISTS OF CHICHIBU. 87 



the very interesting fact that the (juartz here behaves just Uke an 

 isotropic mineral. As this variety fills up the interstitial spaces of 

 the matrix, it is liighly probable that this quartz may be an infiltra- 

 tion-product, and serves as a cement for the other ingredients. AVith- 

 out the use of an upper îs^icol, it is hardly recognizable as such, and 

 a slide presents a perfectly homogeneous appearance; but by the help 

 of an upper Nicol, it is soon discovered that the portion apparently 

 homogeneous resolves itself into numerous crystalline grains of quartz 

 cemented by an amorphous variety. 



Taken as a whole, the quartz in all varieties of rocks of the 

 Sambagawa series is poor in both liquid-inclosures and gas-pores, and 

 such as are found are exceedingly minute in size. These inclosures 

 are arranged in chains, and run approximately parallel to each other, 

 sometimes terminatino- at the margin of the o-rains, or sometimes heiuu: 

 continued on to adjacent grains of different o])tical orientation; some- 

 times again, these chaiiis begin from contiguous points of the neigh- 

 bouring grains, especially "where the margins end in protuberances 

 and indentations. Bearing in mind the facts just stated, these in- 

 closures seem probably to be of a secondary natiu'e. 



The rock now under consideration has possibly assumed the 

 present state through siliceous induration of a graywacke or a volca- 

 nic tuff; hence the colloid aspect of (piartz in it and the paucity 

 of inclosures. The silica may have been derived from the original 

 rock by molecular rearrangement or in part may have come from other 

 sources as a solution, and after the solidification the quartz may have 

 been granulated by mechanical force due to movements of the earth's 

 crust. 



The felspar is very ^ ariable in quantity. In the normal sericite 

 schist from Sueno near Yorii, it is rare; while in that of Ol)oké along 

 the Yosino-gawa, in Awa, it constitutes the main part of the rock at 



