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as follows: oligoclase, 55 percent; muscovite, 17 percent; quartz,

14 percent; chlorite, 2 percent; biotite, 3 percent; clinozoisite, 3 per-

cent; calcite, magnetite, epidote, pyrite, sphene, and other opaque

minerals, 6 percent.

The muscovite schists grade mineralogically into the

chlorite-muscovite schists. An average mineral composition of the

chlorite-muscovite schists, as computed from Hill's (19 39, pp. 55-62)

data, is as follows: albite-oligoclase, 41 percent; muscovite, 17 per-

cent; quartz, 15 percent; chlorite, 15 percent; clinozoisite, 7 percent;

epidote, graphite, sphene, magnetite, and garnet, 1 percent. The most

notable changes that accompany the gradation into chlorite-muscovite

schist are an increase of chlorite and clinozoisite and corresponding

de.creases in the percentage and anorthite content of the plagioclase.

The only notable chemical change is an increase in magnesia and water

associated with minor decrease in amount of the other oxides (table 2).

Graphitic mica schists are present locally in San Francisquito Canyon.

Dark green actinolite-chlorite schists form most of the bulk

of the remainder of the exposed section in Bouquet Canyon. Variations

in composition are not notable. The porphyroblasts of white albite-

oligoclase range in size from one to five millimeters, and in places

they are sufficiently large and abundant to give the schist a distinctly

knotty appearance. As calculated from the petrographic data of Hill

(1939, pp. 63-68), an average mineral composition is as follows:

albite-oligoclase, 44 percent; chlorite, 18 percent; actinolite, 18 percent;