16 
GENERAL GEOLOGY 
On the beach were boulders of granite, vein-quartz, amphibolite, 
hornblende-gabbro, diabase, etc. 
Under the microscope the rocks of this section were found to be as 
follows : 
1. Schists. Quartz-zoisite-schist (47). An extremely fine quartz 
mosaic, with parallel structure produced by sericite and biotite plates. 
Very abundant grains and laths of zoisite, some epidote, and titanite 
surrounding ilmenite. Quartz-epidote-schist (41). Much the same 
as the last, but with more epidote than zoisite, and chlorite as well as 
sericite. 
These rocks may well be altered sediments, but the re crystallization 
is complete and their original character not certain. 
2. Greenstone (45 and 46). Amphibolite. A fine-grained aggre¬ 
gate of hornblende needles, plates of chlorite and sericite, and grains 
of quartz and epidote, with some zoisite. A slight appearance of 
coarse porphyritic structure, as though feldspar phenocrysts had been 
present in the original rock. Probably derived from a diorite-por- 
phyry, or similar igneous rock. 
3. Arkose (44). An aggregate of angular fragments of quartz, 
orthoclase, and plagioclase, cemented with granular quartz, limonite 
and pyrite. All the larger fragments show pronounced cataclastic 
structure and wavy extinctions. 
WRANGELL AND NORTHWARD 
At Wrangell the hill north of the town presents the 
following section (fig. 3): 
FIG. 3. SECTION NORTH OF WRANGELL, ALASKA. 
1. Soft blue slate. 
2. Hard blue slate, with sandy and micaceous layers. 
3. Coarse granitoid metamorphic sandstone (arkose). 
4. Very siliceous biotitic sandstone. 
These rocks, which in the field present the appearance 
of but slightly metamorphosed sedimentaries, give sur¬ 
prising results when studied under the microscope. They 
prove to be highly feldspathic and almost entirely recrys- 
