QUARTZ-BEARING HYPERSTHENE-ANDESINE SYENITE 215 



I. Basic syenite from near Raquette Falls. E. W. Morley, analyst. De- 

 scribed by H. P. Cusbing: New York State Museum Bulletin 115, 

 pages 513-514. 

 II. Augite syenite. Line of townsbips 22 and 23, Franklin County. E. W. 

 Morley, analyst. Described by H. P. Gushing : New York State Mu- 

 seum Bulletin 115, page 514. 



III. Augite syenite, 3% miles north of Tupper Lake Junction. E. W. Morley, 

 analyst. Described by H. P. Gushing : New York State Museum Bul- 

 letin 115, pages 514-516. 



IV. Augite syenite, Ticonderoga. Essex County. M. K. Adams, analyst. 

 Described by J. F. Kemp : New York State Museum Bulletin 138, 

 pages 45-46. 

 V. Augite syenite (akerite), "Loon Lake, Franklin County. E. W. Morley, 

 analyst. Described by H. P. Cushing : Bulletin of the Geological So- 

 ciety of America, volume 10, 1899, pages 177-192. 



VI. Syenite, Whitehall, New York. W. F. Hillebrand, analyst. Described 

 by J. F. Kemp : New York State Museum Bulletin 138, pages 45-46. 



VII. Augite syenite (akerite) from Diana, New York. Description and analy- 

 sis by C. H. Smyth, Jr. : Bulletin of the Geological Society of Amer- 

 ica, volume 6, 1895, pages 271-274. 

 VIII. Quartz-hornblende syenite, one mile northwest of Northville. E. W. Mor- 

 ley, analyst. Described by W. J. Miller : New York State Museum 

 Bulletin 153, pages 14-17. 



IX. Augite syenite, Little Falls, New York. E. W. Morley, analyst. De- 

 scribed by H. P. Cushing : New York State Museum Bulletin 115, 

 pages 514-515, 518. 

 X. Quartz syenite, 2*4 miles south of Willis Pond, Altamont, Franklin 

 County. E. W. Morley, analyst. Described by H. P. Cushing: New 

 York State Museum Bulletin 115, pages 514-519. 



By consulting the table of analyses above of the Adirondack syenites 

 and comparing them with analyses of the Blue Eidge type in table on 

 page 202, it will be seen that in general variation in chemical composition 

 is almost as great for the Virginia type as for the Adirondack type. 

 This variation gains added confirmation when the norms and positions of 

 the rocks in the quantitative system are computed from the analyses. 

 The two types show about equal range in silica, but the Adirondack 

 syenites are richer in alumina and total alkalies than the Virginia rock. 



It is from the mineralogical composition gained from microscopic study 

 of thin sections of the rocks from the Adirondacks and the Blue Ridge 

 that the differences become most apparent. The distinguishing features 

 of the Adirondack syenites are: (1) The feldspars, which make up 50 to 

 80 per cent of the rock, are microperthitic orthoclase and soda-rich plagio- 

 clase, the ratio of orthoclase to plagioclase being variable; and (2) the 

 most prominent mafic mineral is green augite, with sometimes a little 

 hypersthene, hornblende being very common and frequently more abun- 



