ON THE SO-CALLED CRYSTALLINE SCHISTS OF CHICHIBU. 93 



to -which the Avriter wislies to call special attention. It has already 

 been pointed out on page 85, that the quartz forming the matrix ha.s a 

 colloid appearance, and that the felspar-grains apparently corroded 

 at their edge are imbedded in this homogeneous quartz, as if 

 cemented together by a plaster. It may perhaj)s be conveniently 

 called the plastered structure. This differs, hoAvever, from Türne- 

 bohm's ^^ " Miirtel-Structur," by which we understand a fine aggregate 

 of quartz and felspar containing large allomorphic minerals of the 

 same species. 



The upper horizon -) of the Lower division is characterized by 

 a most peculiar rock, viz., tlie piedinontite-schist. 



The next higher — the Middle divisicjn of the Sambagawa series 

 — is essentially formed by an alternation of two distinct types of rocks. 

 These are the spotted (jreeu, and spotted black sclu'sts. The piedmont it c- 

 schist which has just been mentioned commonly occurs iu thin bands 

 in the lower étage of these spotted schists. Nevertheless the writer 

 considers it to be an integral part of the Lower Sambagawan. It 

 will now be shortly described. iSo far as the writer is aware, it 

 has not 3'et been found in other parts of the world, or at least 

 up to the present ncit recorded in any geological literature he has 

 seen, Tliis faft induced the present writer lately to work it out 

 somewhat in detiiil, in a separate ]'aper in this journal Vol. I, 

 part III, t(3 which the reader is referred for the details.^) 



This rock is of a purple coloin-, hence locally calitd the 

 " Murasaki " or purple rock. It is rather more compact than the 

 normal sericite-schist ; but it easily cleaves into thin })lates. On a 

 weathered surface, beautiful purple-red ciyslals of piedmontite or 



1) RosenbuEch ; 'Massige Gesteine,' 2 te Aufl. p. 42. 



2) See Note I iit the end of the paper. 



3) Vide also Quart. Jouru. Geol. Soc., 1887, pp. 474 et 6eq. 



