Washington — Study of the Glaucophane Schists. 47 



California. 



Coining to our own continent, we find glaucophane schists 

 only in the extreme west, where they are extensively developed 

 along the Pacific Coast, in California and Oregon, and possibly 

 beyond these. They are very varied in character, and have 

 been described in part by many geologists, but their relation- 

 ships and origin are not yet fully understood. Some of them 

 would seem to be the products of regional metamorphism, 

 while in other cases they are due to contact metamorphism 

 and are local in character. 



They also vary widely in composition, but the researches 

 already made by others, as well as the analyses given here, 

 show that, just as in Syra, Croatia and Brittany, they belong 

 to two groups, the basic and the acid. As the occurrences are 

 somewhat widespread, they will be described under local head- 

 ings. 



Santa Catalina Island. — The geology of this island, which 

 lies off the coast of Southern California, has been described by 

 W. S. T. Smith. * It is composed largely of diorites and ande- 

 sites, resting on a basement of quartzite and schists, in which 

 also serpentine occurs. 



Of the occurrence of the glaucophane schists he speaks as 

 follows : " Besides the micaceous partings of the quartzites 

 there were found at a number of points partings of blue 

 amphibole, having frequently a silky luster. This amphibole 

 also occurs in larger masses in a schistose condition. The 

 occurrences of this rock are found particularly in the Little 

 Harbor region, apparently confined to the neighborhood of 

 areas of the amphibole, and talc-schists and serpentine. It is 

 probable that here, as elsewhere in California, these blue 

 amphibole schists are due to local contact metamorphism occa- 

 sioned by the intrusion of basic eruptives." 



Dr. Smith does not describe these rocks further, but in the 

 petrographic collection of Yale University is a suite of rocks 

 from Santa Catalina Island, collected by Prof. B. Silliman in 

 1867, among which are several specimens of the glaucophane 

 schists from Little Harbor, on the west coast. I am indebted 

 to Prof. Pirsson for the privilege of studying these, as well as 

 material for analysis. 



They all prove to be quartz-glaucophane schists, pale, blue- 

 gray in color, rather ashy and dull, one fibrous, and the others 

 (including the specimen analyzed), very schistose and fissile, 

 though quite hard. One specimen shows thin bands of white 

 quartz. 



* W. S. T. Smith, Proc. Cal. Acad. Sci., (3), Geol., vol. i, p. 1, 1897. 



