COPPER, ETC., OF PRINCE WILLIAM SOUND. 
79 
Orca was studied, and practically all the copper prospects were examined. On the west- 
ern and northern portions of the sound the work on the general geology was less detailed, 
but nearly all the copper prospects were visited. The present report is a preliminary 
statement concerning the results of this work and treats especially of the copper deposits. 
It is expected that a more detailed report on the general geology and mineral resources of 
Prince William Sound will be issued later. 
Fig. 4.— Sketch map of Prince William Sound region. 
GENERAL GEOLOGY. 
The sedimentary rocks of Prince William Sound consist essentially of graywackes and 
slates. In places the graywackes approach arkoses and sandstones, or even quartzites, 
and the slates approach shales, but three-fourths of the sedimentary rocks of the sound 
can be conveniently and accurately included under the names of graywacke, graywacke- 
slate, and slate. In color these are dark gray or even black, the coarser rocks being 
usually the lightest colored and the slates the darkest. There are a few inconspicuous 
black limestone beds and some conspicuous conglomerates. The latter have commonly a 
coarse graywacke matrix with pebbles of various kinds, among which (1) graywacke, 
(2) fine-grained igneous rocks, commonly rather acidic, (3) flinty slates, and (4) vein 
quartz are the most numerous. In some places the sediments are schistose and more 
crystalline, but no markedly crystalline schists occur except in the immediate vicinity of 
granitic intrusions. 
