:',,sn The American Geologist. June, i«96 
albitite. Other dikes in the immediate neighborhood of the 
albitite dikes contain quartz in addition to the feldspar, form 
ing ;i soda-granulite, as the term is used by Michel Levy, or a 
soda aplite, following Rosenbusch. In the serpentine area of 
( J-rizzly hill ( Hi dwell Bar sheel ) are numerous dikes of a soda- 
granulite containing muscovite in addition to the quartz and 
albite (see No. 725, S. N., table of analyses.) 
There are also numerous soda-feldspar dikes northwest of 
Meadow valley in serpentine by the trail to Rich Bar. Those 
noted were chiefly finer grained than the dikes above men- 
tioned. 
The large serpentine area to the southeasl of Meadow valley 
that contains the soda-feldspar dikes above mentioned is 
Hanked for considerable stretches by areas of a coarsely 
fibrous dark green hornblende-schist. One of these masses 
lies on the west flank of Clermont hill. In it are veins of a 
peculiar blue quartz. (No. 458 Plumas.) Another area is 
crossed by the south fork of the Feather river to the east of 
Little Grass valley. In it are dikes of a coarse grained rook 
(No. 97 S. N. ) composed of a very white feldspar, pretty cer- 
tainly albite. and the same peculiar blue quartz that occurs 
without any feldspar in the hornblende-schist of Clermont 
hill suggesting a genetic connection between the blue quartz 
veins, and the soda-granulite and soda-syenite dikes just des- 
cribed. The hornblende of the schist is an aluminous variety, 
containing about 48 c / r of silica. 
In another paper* altered porphyry dikes composed chiefly 
of albite were described as forming the lodes of the Shaw and 
Orofino mines (the latter now called Big Canyon mine) in 
Eldorado county (Placerville sheet). In the table of analyses 
No. 452 S. N. is an analysis of the Shaw mine dike. 
The feldspathic nature of the Shaw mine lode was sugges- 
ted by Mr. C. A. Aaron f in 1892. This article was not refer- 
red to by the writer in the paper in the American Journal of 
Science, as it was not then known to him. A portion of Mr. 
Aaron's article is here quoted, to give a better idea of the 
economic value of the lode. 
*Am. Jour. Sci., 3, vol. xlvii, 1894, pp. 470-471. 
tEng. and Min. Jour.. November 19, 1892. 
