12 Canadian Record of Science. 



shows distinct cleavage, is clear and colorless, and occurs 

 in irregularly shaped masses near the feldspars or the 

 biotite, though it does not appear to have been derived 

 from the latter ; occasionally it presents the fibrous or 

 plumose structure of sericite. What points most strongly 

 to its origin is its occurrence in the feldspars in detached 

 particles, which, however, are parts of large individuals, 

 giving simultaneous extinction and hence being similarly 

 oriented. They are really skeleton crystals which have 

 been formed at the expense of the feldspar. Similar 

 phenomena have been noticed in granites from the Pelly 

 Eiver, British Columbia, 1 and in the Stanstead 2 granite in 

 Quebec. Both these granites resemble in other ways the one 

 under consideration ; both have been subjected to intense 

 pressure while deep in- the earth's crust, and in the latter 

 case, the orthoclase has been converted into microcline 

 just as in this one. The muscovite seems to have been 

 produced by the same forces which caused these other 

 changes, and indicates a first stage of dynamic metamor- 

 phisra. short of complete recrystallization. 3 The magnetite 

 is frequently altered about the edges to limonite, which 

 has infiltrated along the cleavage-planes of the feldspars. 

 The zircon is in small, well-defined prismatic crystals, 

 terminated by a combination of pyramidal forms which 

 gives an almost rounded appearance. It has a broad, 

 black boundary, denoting high refractive index, and very 

 high double refraction, polarizing in pale blue tints. The 

 apatite is also in well-formed crystals, of hexagonal out- 

 line, low index of refraction, and low double refraction, 

 giving bluish gray in polarized light. 



The structure of the rock is granular and allotrio- 

 morphic. 



1. Adams, F. D., " On Some Granites from British Columbia, etc." Can. Rec. Sci., 

 IS91, Vol. IV., pp. 352-354. 



2. Adams, F. D., "Description of a Series of Thin Sections of Typical Rocks," 

 Montreal, 1S96, pp. 5-6. 



3 cf. Harker, A., " Petrology for Students," Cambridge, Eug., 2nd ed., 1897, p. 309. 



