2 4 
ALASKA GEOLOGY 
magnetite grains, crystals of green mica, and abundant grains and 
prisms of epidote. A rock of uncertain origin. 
Quartz-biotite-diorite (189). Snow-white feldspars with large 
sharp crystals of biotite. 
Gneissoid biotite-granite (193). A fine-grained greyish granite 
with distinct banding brought about by parallelism of biotite plates. 
Black micaceous quartzite (277). 
With these crystalline rocks are probably to be grouped other boul¬ 
ders found on the shores of Yakutat Bay—coarse crystalline marble 
with black veins (292), coarse pegmatite with felted actinolite needles 
(291), poikilitic mica-diorite (279), and fine-grained epidote-chlorite- 
schist (278). 
PRINCE WILLIAM SOUND 
As in Yakutat Bay so also in Prince William Sound we 
found the rocks to consist mainly of the sandstones and 
shales of the Vancouver Series or of the closely similar 
Valdes Series of Schrader. Reference will be made to 
these later, in the section devoted to these rocks. At 
Landlocked Bay and at Virgin Bay the rocks seemed to 
have a different character. We went ashore at Land¬ 
locked Bay, the vertical walls of which shut us in 
like a well, and climbed several hundred feet over a 
wall of serpentine to the adit of a copper mine. The de¬ 
posit of copper ore is a mass of quartz, with chalcopyrite, 
pyrrhotite, and small amounts of galena and sphalerite, oc¬ 
cupying a shear zone in a rock of serpentinous charac¬ 
ter. Thin sections of this rock (186) showed a mass of 
fibrous serpentine in which are embedded shattered crys¬ 
tals of perfectly fresh labradorite and abundant augite, 
raveled out on the edges to colorless hornblende and 
serpentine. There are still traces of ophitic structure, and 
the rock is evidently a sheared and partly serpentinized 
diabase. 
At Virgin Bay we found the rocks at the shore for 
a great thickness impregnated with pyrite and chalcopy- 
