Washington — Study of the Glaucophane Schists. 45 



Epidote- Glaucophane Schist. — One of these specimens is a 

 rock of this character from Iiongo, in Norimoto Village, 

 Yana District, Province Mikawa. It is compact, of a rather 

 dark, greenish gray color, and schistose with a silky luster. 

 The specimen is traversed by a vein of calcite, which was 

 avoided in the material chosen for analysis. The microscope, 

 as well as the analysis, shows that this mineral is present 

 throughout the rock to a considerable extent. 



The structure of the rock as seen by the microscope differs 

 from most of the other specimens examined, in the very finely 

 fibrous character of the glaucophane, which is rather pale, but 

 of the usual pleochroism. This forms streaks and bands 

 through the rock, bringing out the schistose structure, and also 

 occurs as a sort of felt. With it, but somewhat locally devel- 

 oped, is a pale green or bluish-green, not highly pleochroic, 

 amphibole, also in needles, which seem to be an actinolite and 

 to be derived from the glaucophane. A yellowish epidote 

 occurs in small grains, chiefly intimately associated with the 

 glaucophane. 



Partly intermingled with these three, but generally forming 

 the greater part of separate streaks, is a colorless mineral of 

 rather high refraction and low birefringence, the polarization 

 colors being grays and blue-grays. It is chiefly in long grains, 

 not showing much cleavage, and is apparently orthorhombic. 

 This must be referred to zoisite, as the low alkalies preclude 

 the possibility of its being a feldspar. Calcite is quite com- 

 mon, and some grains of quartz are seen. Titanite is also 

 present in small grains. 



The analysis of this rock, given in I below, is that of a nor- 

 mal epidote-glaucophane schist, with high CaO. It calls for 

 no special remark here. 



A specimen of glaucophane schist from Otaki-san, near 

 Tokushima, Shikoku Island, represents the rocks in which 

 glaucophane was first discovered in Japan by Koto, and which 

 have been briefly described by him. The majority of them 

 would seem to be epidote-glaucophane schist, some containing 

 garnets, but the one in my possession is a quartz-glaucophane 

 schist. Unfortunately it is seemingly so badly altered that no 

 analysis was made of it, but a brief description may be of 

 interest. 



It is a highly fissile, schistose rock, of a general brownish 

 color, glistening with mica scales, and with abundant dark 

 blue glaucophane. Microscopically it is composed of stout 

 prisms of dark glaucophane, white mica, and considerable 

 interstitial quartz. Small crystals of colorless titanite, apatite 

 and zircon (?) are numerous. Brown limonitic stains over all 



