Granites from British Columbia, etc. 351 



In his report, Dr. Dawson refers to this granite as follows : 

 (p. 132). 



"Nine miles above the confluence, by the course of the 

 river, a great mass of impure serpentine comes out on the 

 bank, and six miles and a half above the same place, grey 

 granite of the usual character is again met with and appears 

 to constitute the hills to the east of the river for the 

 remaining few miles of its course." It is a grey muscovite 

 biotite granite of miduum grain. There is a barely percep 

 tible parallelism visible in the arrangement of the constit- 

 uents, so that it might possibly be termed a granitic 

 gneiss. It consists of the following minerals, quartz, ortho- 

 clase, microcline, plagioclase, muscovite, biotite, epidote, 

 garnet, calcite, sphene and pyrite. The quartz and ortho- 

 clase constitute a large proportion of the rock, while the 

 plagioclase, micas and other constituents are less abundant. 

 The quartz and feldspar are sometimes broken and 

 show uneven extinction, in fact the rock seems to have 

 been considerably crushed, but I can see no evidence of 

 anything like complete re-crystallization. The biotite is 

 not very abundant and is sometimes partly altered to 

 chlorite. The garnet, which like the sphene and pyrite is 

 present in small amount, occurs in irregular shaped isotropic 

 grains which are much cracked. The epidote, muscovite, 

 and calcite, however, are of especial interest. 



The epidote is the normal variety with one good cleavege 

 at right angles to the plane of the optic axes and generally 

 possesses a faint pleochroism, colourless and greenish 

 yellow. It occurs occasionally in fairly perfect crystals, 

 but is frequently found in the same curiously imperfect 

 forms which it assumes in Wrangell Island rock. The little 

 arms and bays which run into these epidote individuals 

 are sometimes quartz. In very many cases, however, they are 

 feldspar (plagioclase) as indicated by the biaxial figure and 

 polyoynthetic twinning, the included portions being con- 

 tinuous and having the same optical orientation as the 

 feldspar surrounding the epidote, being in fact, a portion 

 of the same individual. The muscovite is rather more 



