Washington — Study of the Glaucophane Schists. 53 



appearance it is not unlike the intermediate mica-glaucophane 

 schist from Cafe Skarbeli, Syra, already described. In thin 

 section it is seen to be composed very largely of quartz, which 

 shows clear evidence of crushing. In this lie well-formed 

 glaucophane prisms, which are highly pleochroic, c blue, b 

 violet, a pale yellow or colorless. With these, but in less 

 amount, are thin flakes of colorless mica, which the analysis 

 shows to be muscovite scales and plates of chlorite, and some 

 small garnets. 



The analysis (II) shows an exceedingly acid composition, 

 being the highest in Si0 2 of any of the rocks so far examined 

 by me. On calculation the mineral composition works out as 

 follows : 



Quartz 67*6 



Glaucophane 14*2 



Muscovite 10*4 



Garnet 



Chlorite 



100-0 



The relatively high K 2 in both these Oregon rocks is note- 

 worthy, the nearest approach to them in this respect being the 

 " glaucophane slate" of Kamoi Kotan in Japan. 



I. II. III. 



Si0 2 46-07' 82-53 49'15 



A1 2 3 15-35 6-88 15-87 



Fe 2 3 3-61 0-59 4-10 



'FeO 9-87 4'11 7-58 



MgO .._ 7-83 1-86 7'53 



CaO -. 4-37 0-68 9'06 



Na 2 3-22 1-21 3'59 



K 2 ... 2-68 1'24 0-54 



H 2 OllO°+ 4-25 1-35 1-07 



H 2 110°— 0-16 0-07 0-16. 



C0 2 1-05 none 



Ti0 2 1-63 1-19 



MnO trace trace trace 



100-09 100-52 99*84 



I. Epidote-glaucophane schist. Near Winston's Bridge, Rose- 

 burg, Douglas Co., Oregon. Washington anal. 

 II. Quartz-glaucophane schist. Four Mile Creek, Coos Co., 

 Oregon. Washington anal. 

 III. Garnet-glaucophane schist. Tupper Rock, near Brandon, 

 Coos Co., Oregon. Washington anal. 



