III.] THE CHEMISTKY OF METAMOKPHIC EOCKS. 31 



unknown in more recent formations, and are associated with 

 veins of crystalline apatite, which sometimes attain a thick- 

 ness of several feet. The serpentines of this series, so far 

 as yet studied in Canada, are generally pale- colored, and 

 contain an unusual amount of water, a small proportion of 

 oxide of iron, and neither chrome nor nickel ; both of which 

 are almost always present in the serpentines of the third 

 series.* 



The second or Labrador series is characterized, as already 

 remarked, by the predominance of great beds of anortholite, 

 composed chiefly of triclinic feldspars, which vary in compo- 

 sition from anorthite to andesine. These feldspars sometimes 

 form mountain masses, almost without any admixture, but at 

 other times include portions of pyroxene, which passes into 

 hypersthene. Beds of nearly pure pyroxenite are met with 

 in this series, and others which would be called hyperite and 

 diabase. These anortholite rocks are frequently compact, but 

 are more often granitoid in structure. They are generally 

 grayish, greenish, or bluish in color, and become white on the 

 weathered surfaces. The opalescent labradorite-rock of Labra- 

 dor is a characteristic variety of these anortholites ; which 

 often contain small portions of red garnet and brown mica, 

 and more rarely, epidote, olivine, and a little quartz. They 

 are sometimes slightly calcareous. Magnetic iron and ilmenite 

 are often disseminated in these rocks, and occasionally form 

 masses or beds of considerable size. These anortholites con- 

 stitute the predominant part of the Labrador series, so far as 

 yet examined. They are, however, associated with beds of 

 quartzose orthoclase-gneiss, which represent the first class of 

 aluminous sediments, and with crystalline limestones ; and 

 they will probably be found, when further studied, to offer a 

 complete lithological series. These rocks have been observed in 

 several areas among the Laurentide Mountains, from the coast 

 of Labrador to Lake Huron, and are also met with among the 



* See in this connection the author on the History of Ophiolites, Am. 

 Jour. Science (2), XXV. 117, and XXVI. 234. 



