GEOLOGY OF MOUNT MARCY 43 



(Opus cit., p. 236) " In the rocks which we are studying, it seems 

 difficult to admit that the garnet should be only formed along the 

 contact with the hornblende gneiss." 



The first mention of garnet rims in the Adirondacks that has come 

 to the writer's notice is in the paper by A. R. Leeds, " Notes upon 

 the Lithology of the Adirondacks/ " 



In describing a specimen he says, " Garnet is not unfrequently dis- 

 posed as a red border around the greenish masses of diallage, along 

 the bounding surfaces between it and the labradorite." No theory of 

 their formation is mentioned. 



Since Professor Leeds's paper, garnet rims from the Adirondacks 

 have been described by J. F. Kemp^ and W. J. Miller^ in various 

 articles. 



This list does not claim to be a complete one, but gives those arti- 

 cles which have been of particular interest to the writer. J. F. 

 Kemp, in the article on the titaniferous iron ores, speaks of an 

 occurrence in gabbro which " has been somewhat squeezed, so that 

 secondary garnets have been developed in quantity." W. J. Miller 

 (op. cit., p. 30 and 31) describes several rims, some of garnet, others 

 lacking the garnet and composed entirely of other ferromagnesian 

 minerals. He designates them as " reaction or corrosion rims " and 

 also says that " Garnet is almost invariably in contact with feldspar 

 which suggests the partial formation, at least, of the garnet from 

 feldspar." 



Another occurrence of garnet that must be mentioned in this con- 

 nection is that described by F. Zirkel.* In this case the garnet occurs 

 not as rims but as aggregates in a basalt, and has been regarded as 

 primary. 



The study of the specimens and the literature suggested four possi- 

 ble modes of formation for the garnet rims: (i) that these lenses 

 represented stoped-in fragments of the rock invaded by the anortho- 

 site and metamorphosed to pyroxene-garnet masses; (2) that the 

 garnets were primary and the zonal arrangement due to the order 

 of crystallization; (3) that in this particular case there had been an 

 addition of silica due to an aplitic invasion; (4) that the garnets 



1 Thirtieth Ann. Rep't, N. Y. State Mus., 1876. 



2 J. F. Kemp, " Gabbros on the Western Shore of Lake Champlain," Bui. 

 Geol. Soc. America, v. 5, p. 217-21, 1894. 



J. F. Kemp, " The Titaniferous Iron Ores of the Adirondacks," pt 3, 

 19th Ann. Rep't, U. S. Geol. Surv., 1897-98. 



^ W. J. Miller, " Geology of the North Creek Quadrangle, Warren County, 

 New York." N. Y. State Mus. Bui. 170, 1914. 



4" Uber Urausscheidungen in Rheinischen Basalten," Leipzig, 1903. 



