48 Washington — Study of the Glaucophane Schists. 



Under the microscope the specimen analyzed shows a multi- 

 tude of fine, pale blue glaucophane needles, and larger crystals 

 fringing out into needles, embedded in granular quartz, with 

 some minute zircons and a few grains of epidote. There is no 

 carbonaceous matter present, but in another similar specimen 

 this exists to a considerable extent, while a dark, compact rock, 

 also from Little Harbor, is a black and apparently little altered, 

 quartzose shale. 



I. II. in. 



SiO Q __ 74-48 80-21 74-16 



A1 2 3 9-15 7-99 11-85 



Fe 2 3 1-41 0-82 



FeO 4-12 3-35 1-66 



MgO 3-04 1-54 2-10 



CaO 2-84 1-10 2-10 



Na 2 2-24 5-97 6-57 



K 2 G 0-43 0-22 0-15 



H 2 Oll0°4- 2-06) ~»A i ' 52 



H 2 110°- 0-08 f °' 4 j 0-05 



C0 2 _ .... .... 0-09 



Ti0 2 . ... .... .... 0-37 



P o 5 .... 0-08 



MnO ... 0-06 



C _ 0-18 



101-12 



100-7i 



I. Quart z-glaucophane schist. Little Harbor, Santa Catalina 



Island, Cal. Washington anal. 

 II. Quartz-glaucophane schist. Angel Island, Cal. Ransome 

 anal. Bull. Dept. Geol. Univ. Cal., vol. i, p. 231. 

 III. Adinole, Mansfield, Mich. Steiger anal. Clements. This 

 Journal, vol. vii, p. 88, 1899. 



The analysis shows that quartz is very abundant, more so 

 indeed than the microscopical examination would have led one 

 to suppose. It is possible, to judge from the amount of A1 2 3 , 

 that sillimanite is present, since Smith speaks of it as occurring 

 in the neighboring quartzite. None was seen in the sections, 

 though the dense felt of glaucophane needles would make its 

 identification difficult. 



It may be inferred from the presence of carbonaceous mat- 

 ter in some of the specimens, and from the apparent gradation 

 to true shale shown by them, that these schists are derived 

 from shales of a quartzose character, or from the quartzites as 

 Smith suggests, possibly through the contact metamorphism 

 of intruded igneous rocks. 



It may be mentioned that the analysis corresponds very well 

 with that of an adinole (III above), derived from a clay slate 



