.'{74 



University of California. 



[Vol. 3. 



constitutes nearly one half of the mineral constituents. A few 

 large phenocrysts of feldspar occur, portions of the interior of 

 which exhibit mierographic intergrowth. The feldspar of the 

 second generation occurs in rather poor laths and shapeless 

 patches which usually show an u minions extinction. Inclusions 

 of hornblende occur. 



The dominant feldspar is a plagioclase whose exact character 

 remains indeterminate. The other specimen of camptonite from 

 one of two small dykes at the north end of Upper Kern Lake is 

 a ('(impact, fine grained, dark rock containing numerous pheno- 

 crysts of hornblende. The structure is holoerystallme with a 

 strong porphyritie development of green hornblende. Apatite 

 needles are abundant. The hornblende makes up nearly 75 per 

 cent, of the rock. It occurs in two generations; those of the 

 first producing large basal and prismatic sections; those of the 

 second crystallizing in slender prismatic forms. A strong tend- 

 ency to separate out iron oxides exists. The feldspar is small in 

 amount and occurs as sporadic laths showing albite twinning, 

 and as patches, often polysomatic. 



Lava of the Little Kern Plateau. — Two specimens of this lava 

 were examined. One is a fine grained lava of gray color con- 

 taining an occasional small vesicle. Under the lens the structure 

 is seen to be the typical "intersertal" of Rosenbusch. The 

 dominant constituent is plagioclase developed in sharp idiomor- 

 phic laths of almost microlitic dimensions. This abundance of 

 feldspar controls the structure, and forces the augite and 

 magnetite granules to occupy the triangular spaces between the 

 laths. The plagioclase microlites show strong albite lamellation, 

 and yield extinction angles of 30? This determines them as acid 

 labradorite. Augite is present in large amount in the form of 

 granules only, never exhibiting crystal boundaries. The augite 

 is often red from iron oxide stains. The rock maybe classed as 

 a non-oliventic basalt. 



The other specimen of lava from the Little Kern Plateau is an 

 exceedingly fine grained, gray lava showing occasional minute 

 vesicles. Microscopically the rock resolves into a pilotaxitic 

 ground composed of augite microlites and granules, plagioclase 

 microlites, and grains of magnetite. Occasional patches of feld- 



