ON THE SO-CALLED CRYSTALLINE SCHISTS OF CHICHIBU. 



95 



(S = brownish-red ; S = light-violet. The Pleochroi^m is distinct, 

 the polarization-colours magnificent. 



Being of a beautiful rosy-red colour, highly pleochroic and acicu- 

 lar in habit, it has been called by Dr. E. Naumann a tourmaline, i) 



The piedmontite is capable of undergoing various modifications. 

 On the one side it forms a transition into a greenish-yellow epidote, the 

 same one described in connection with the normal sericite-schist 

 (ante page 90) but Avith this ditference that here the red pigment 

 localizes itself in the centre or in irregular patches. It is a most 

 peculiar fact that the purple piedmontite also graduates into an almost 

 colourless epidote. This abnormal, colourless epidote is found in long 

 stalky crystals with rather fibrous terminations at both extremities, 

 and is not unlike a broad column of Graiumatitc. AVhat the chemical 

 nature of this epidote is, the writer cannot at present say. Anyhow 

 he is not disposed to consider it as a variety of zoicite. 



The Jteiiiatite is represented by the blood-red hexagonal plates 

 of iron-mica whose minute scales are found aliundantly in the greenish- 

 yellow, and also in the colourless epidote ; while another variety 

 (iron-glance) is comparatively rare and occurs in the form of dull, 

 opaque clumps. Thus the habitus of iron-glance deviates somewhat 

 from that of the normal sericite-schist. The presence of iron-mica 

 gives a considerable reddish tinge to this purple schist. In pied- 

 montite, iron-glance is never found as interpositions. 



The felspar occurs exclusively as grains without anv sign of idio- 

 morphic forms, and commonly larger in size than those of the quartz. 

 It is intimately intergrown with the latter as if the felsjiar served as a 

 cementing medium, thus producing the plastered structure. The inter- 

 position of quartz-grains is of com.mon occurrence — a fact illustrative 

 of the simultaneous crystallizati(m of both minerals. Simple twins 



1) Loc. cit. p. 10. 



