368 The American Geologist. •'""*^' i'^05 
iginal zone nearer the former surface. In support of this 
theory are advanced: (i) the evidences of great erosion 
shown in and about the Pala valley, (2) the more basic 
nature of the rocks, according with deeper seated condi- 
tions, (3) the occurrence of the heavy minerals — garnet and 
triplite — and especially of the suphide of bismuth, (4) the 
shape of the noryte area, more resembling a neck or boss 
than a dyke. The occurrence of epidote and fibrolite — sec- 
ondary minerals typical of the zone of katamorphism — in 
the Eallbrook, but not in the Pala region, is another point 
in support of this theory. Of the two hornblende granu- 
lytes studied, occurring as small dykes in the country rock, 
that from Pala shows more tendency toward recrystalliza- 
tion of the minerals, than does the Fallbrook rock, also in- 
dicating a greater depth of formation for the former. The 
general occurrence of potash feldspar in the triclinic form, 
microcline, may be taken partly as an evidence of pressure 
due to depth, though it is the usual variety occurring in 
pegmatytes. Several minerals show the effects of crushing 
and slight displacement, as black tourmalines and crossed 
plates of mica. The fresh granulated feldspar -also shows 
the results of crushing. Evidently considerable orographic 
movement has caused this. 
Alterations of the Minerals. Since the time when ero- 
sion brought the present accessible part of the veins above 
the zone of anamorphism considerable alteration of the min- 
erals has taken place. The spodumene is often fractured 
and pitted and contains patches of kaolin-like material. 
The alteration to beta-spodumene and finally to muscovite 
and albite as in the Branchville, Conn, variety is not shown 
in thin sections of the Pala mineral. The decomposition of 
rubellite to halloysite has been mentioned. Vermiculite 
occurs to some extent as an alteration of the mica, especi- 
ally at Rincon. The alteration of microcline and albite to 
kaolinite and muscovite with the liberation of silica and the 
alkaline carbonates seem to take place to considerable ex- 
tent, and is thought to be the origin of the clay of the 
pockets. These reactions take place with a decrease in 
volume of from 5% to 16%, assuming the silica to crystal- 
lize as' quartz and the carbonates to be carried off in solu- 
