ALASKA-TREADWELL MINE 65 



suggesting a variety allied to glaucophane. Patches of 

 the rock are wholly made up of granules of bright green 

 epidote, which give a greenish mottling to the hand speci- 

 men. Cloudy areas full of minute black specks which 

 may be magnetite are numerous. Numerous round or 

 oval spots in the section, lined with quartz or feldspar and 

 rilled in with grains of calcite, strongly suggest amygda- 

 loidal cavities in a lava; and it seems quite likely that the 

 schist represents a completely metamorphosed eruptive 

 rock. 



In the canyon of Gold Creek immediately back of Ju- 

 neau was found a series of greenstone schists of consider- 

 able extent. Of the many varying phases seen in this 

 series the following varieties were collected: 



No. 22, actinolite-schist, a very compact fine-grained schist of 

 light green color, showing many slickensided surfaces covered with 

 chlorite. In the section it is seen to be composed almost wholly of 

 rather short prisms of actinolite, with quartz grains filling the inter- 

 spaces. A little epidote in small grains and an occasional titanite 

 grain are also present. 



No. 23, actinolite-schist ', very like the last, but charged through- 

 out with minute and very sharp octahedrons of magnetite. 



No. ^i, actinolite-schist, the surface showing oval areas of chlorite, 

 which give it a spotted appearance. 



No. 25, schistose diorite-forphyry (actinolite-schist), a rock of 

 schistose texture but distinctly porphyritic with white dots in the 

 greenish matrix. Under the microscope the porphyritic spots appear 

 as sharply marked areas containing aggregates of needles of zoisite 

 and actinolite, with quartz filling the interspaces. The groundmass of 

 the rock is a finely felted aggregate of actinolite needles with epidote 

 and quartz grains. The appearance indicates pretty certainly the deri- 

 vation of the rock from a diorite-porphyry by dynamic metamorphism. 



In the schists are occasional quartz lenses in which are 

 siderite and granular epidote and at times masses of fine 

 scaly chlorite (delessite). 



At one point on the road a dike of aplite was found, 



