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University of California Publications in Geology [Vol. 13 



One of the quartz-pyroxene rocks carries a small amount of green 

 hornblende. Examples of quartz-amphibole rocks, carrying no pyrox- 

 ene, were found at two localities, and differ in no way from the quartz- 

 pyroxene rocks save in the substitution of green hornblende for diop- 

 side. The hornblende of these rocks is a green-brown variety. The 

 pleochioism is a = colorless to faint green, h = brown, c = green, ab- 

 sorption : 6 > c > a. 



One of the dense quartzose lenses, occurring in sillimanite gneiss, 

 is composed of about 85 per cent quartz, the balance being basic 

 plagioclase with a small amount of biotite. 



The writer has been unable to find any reference to rocks similar 

 to these lenses in American geologic literature. Harker and Marr 

 have described the metamorphic effect of the Shap granite on the 

 Lower Coldwell grit in Westmoreland. The unaltered rock is com- 

 posed of subangular grains of quartz and feldspar, with some inter- 

 stitial dusty matter like kaolin, and little patches of finely granular 

 ealcite. A specimen of the metamorphosed rock, from 600 yards from 

 the granite contact, has a vitreous appearance and is made up of 

 quartz, feldspar, and lime augite, the contacts of the minerals being 

 "sutural." 2 



Rosenbusch has described a number of quartz-pyroxene rocks from 

 Alsace and southern Germany. They are classed in his para-pyroxene 

 gneiss group, within which there is a wide range of mineralogic com- 

 position. 3 



With regard to the structure of these rocks he states: 4 "While 

 the ortho-pyroxene-gneisses are usually distinctly schistose, this is very 

 often not the case with the para-pyroxene-gneisses and their structure 

 is typically hornfels-like." 



A typical section through the schist series. — The following is a 



section from the northeast edge of the main schist mass, immediately 



west of Banner, southwest ward to the Julian-Cuyamaca road : 



Giieissoid granodiorite. 

 60 feet Injection gneiss. 

 300 feet 1. Quartz-two-miea schist with knots of muscovite. Coarser near 

 the igneous contact, grades into next member away from contact. 

 700 feet 2. Medium grained quartz-mica schist, with quartzite layers. 

 400 feet 3. Medium grained quartz-two-miea schist. Large muscovite flakes 

 at high angle to schistosity. "Boiled" lenses of quartz-pyrox- 

 ene rock. 



2 Harker, A., and Marr, J. E., Quart. Jour. Geol. Soc, vol. 47, 1904, p. 321. 



3 Kosenbuseh, H., Elemente der Gesteinslehre, 1910, pp. 617-619. 

 * Ibid., p. 618. 



