Geological Notes on the Sierra Nevada. — Turner. 303 
follows very closely the strike of the strata and when they 
bend very perceptibly to the northwest, as is the case from 
Clermont hill in Plumas county to Meadow valley and beyond, 
this dike likewise has the same northwesterly course. The 
serpentine at Red hill in Plumas county to the north of the 
fortieth parallel is a part of this dike, which extends south 
from that point at least fifty miles. The serpentine of 
Goodyear's bar in Sierra county belongs to the same 
area. This dike-like serpentine area has a width where 
it is crossed by the middle fork of the Feather river of more 
than three miles. Associated with the serpentine are large 
amounts of amphibolite-schist. This is especially abundant 
to the south of Onion valley in Plumas county. It seems at 
some points to replace the serpentine, which occurs sometimes 
to the east and sometimes to the west of the amphibolite. and 
sometimes, as two miles south of Onion valley, the serpentine 
is bordered on both sides by a belt of amphibolite-schist. To 
the north of the middle fork of the Feather river the amphib- 
olite-schist is coarsely fibrous and forms a very definite belt 
one-half mile or more wide to the east of the broad serpentine 
dike, and a much broader belt is cut by Slate creek in Siena 
county. The relations of the two frocks are beautifully 
shown on the south and west slopes of Clermont hill, and 
there the contact of the two is everywhere sharp. 
11 is presumed that there is a genetic relation between the serpentine 
and the amphibolite-schist, but exactly what the relation is. has not 
vet been determined. It was first shown by Mi'. .1. S. Diller* thai the 
original rock of this serpentine dike was a peridotite or allied pock, and 
the writer found some pyroxenite in the middle of the dike on the ridge 
to tin' south of the middle fork of Feather river, and also in Sierra 
county near Goodyear's creek. 
[n this serpentine belt to th'e southeast of Meadow valley at various 
points are small dikes of a verj white rock. The microscope shows 
these to be made up almost wholly of large grains of feldspar with 
marked cleavage, and showing occasionally a twin lamella. From the 
following partial analysis by professor Hillebrand of a specimen from a 
dike between the junction of Rock and Deer creeks it seems unques- 
t ionable that t he feldspar is albite: 
Analysis ok No. J.V>. Plumas County. 
SiO., 66.54 
Mgo ;; 
CaO 13 
K 2 89 
N a O 10.28 
*Eightli Ann. Rep. I'. S. (ieol. Survey, p. 106. 
