14 F. D. Adams — Nejpheline Syenite in Ontario. 



composed the scapolite was found to be still quite fresh. The 

 uniaxial and negative character of the mineral together with 

 the position of the cleavages, the strong double refraction, the 

 parallel extinction and the deportment with acid, proves that 

 the mineral is really scapolite. 



( 'alcite. — The presence of this mineral in such a rock, as 

 well as its mode of occurrence is very remarkable. The rock 

 is quite fresh so that the calcite is not an ordinary decomposi- 

 tion product. Its mode of occurrence is that of an original 

 constituent. It is found in well defined, more or less rounded, 

 individuals, often of large size, occurring with, and often in, 

 the other constituents of the rock. It has been observed com- 

 pletely enclosed by hornblende, nepheline, plagioclase, and 

 garnet, the boundaries of the several minerals being quite 

 sharp and the enclosing mineral being quite unaltered and 

 normal in character. It shows the usual rhombohedral cleav- 

 ages, is frequently twinned and sometimes has a fairly good 

 crystalline form. It occurs in almost every slide, though 

 usually in comparatively small amount. Individuals of con- 

 siderable size are found in the very coarse grained variety of 

 the rock at the York River. The origin of this calcite is a 

 point which it is difficult to determine, although somewhat 

 similar occurrences have been described in various other igne- 

 ous rocks.* It cannot be a decomposition product in the ordi- 

 nary sense of the term. Its mode of occurrence does not 

 seem to indicate that it fills miarolitic cavities as Kosenbusch 

 has supposed similar occurrences in certain granites to do. 

 Had it been derived from the neighboring limestones some 

 evidence of corrosion or alteration might be expected from 

 the action of the very acid magma. Further study in the 

 field may throw additional light on the question. 



Garnet. — This is of a pale brownish or reddish-brown color 

 and is always quite isotropic. It occasionally has a good crys- 

 talline form but usually occurs in more or less irregular shaped 

 grains. It is present in most slides but seldom in large quan- 

 tity- 



Zircon. — Occurs in many slides and occasionally in the 

 coarser variety of the rock in crystals of considerable size. 



Socialite. — At a number of places sodalite was observed in 

 small grains or strings, scattered through the rock and it 

 appears in one or two of the slides. 



In certain parts of the area however it occurs in large masses. 



* A. E. Tornebohm, " Out kalcithalt i graniter." Geol. Foren. i Stockholm 

 Forh., 1882, 140. G. W. Hawes, " Mineralogy and Lithology of New Hamp- 

 shire," p. 207. See, also, F. D. Adams, "On some Granites from British Columbia 

 and the adjacent parts of Alaska and the Yukon District." Canadian Record of 

 Science, Sept., 1891. 



