254 H. W. TURNER GEOLOGY OE THE SILVER PEAK QUADRANGLE 



to such completely crystalline rhyolitic lavas the term micro-granite is 

 sometimes applied. 



Some of the meta-rhyolites contain microperthite. There is thus a 

 considerable variety of rocks, especially dike rocks, included on the geo- 

 logical map under the term meta-rhyolite. 



Partial Analyses of Soda Meta-latite, Meta-rhyolite and Eeratophyre 

 George Stciger, Analyst 





Number 

 319. 



Number 

 343. 



Number 

 313. 



Silica. 



56.34 

 4.0L 

 6.32 

 2.63 



68.40 

 2.83 

 9.00 



none 



80.60 



Lime 



.18 



Soda 



6.04 



Potash 



none 







Felsitic rock, specimen number 319. — Locality: In the Palmetto mountains, 

 11.7 kilometers southwest of Barrel spring. 



Macroscopically, a fine grained flinty rock, slightly brownish in color. 

 Microscopically, a felsitic rock of undetermined composition, filled with sec- 

 ondary products. The chemical composition is that of an alkali-rich andesite 

 or latite. 



Soda-syenite-porphyry or keratophyre, specimen number 343. — Locality: 

 Dike in the Ordovician cherts of the Palmetto mountains, 5.5 kilometers 

 southwest of Barrel spring. 



Macroscopically, a light colored, slightly brownish rock showing porphyritic 

 feldspars. Microscopically, a porphyritic rock with a micro-granular quartz- 

 feldspar groundmass in which are prisms of albite and oligoclase. Monoclinic 

 pyroxene is rather abundant, and there is a secondary mineral, apparently 

 epidote, present. 



Soda-meta-rhyolite or quartz-keratophyre, specimen number 313. — Locality: 

 Dike in Lower Cambrian rocks, 2.6 kilometers southeast of Barrel spring. 



Macroscopically, a nearly white, fine grained, apparently noncrystalline 

 rock. Microscopically, a porphyritic rock with a micro-granular quartz-albite 

 groundmass crowded with spherulites and phenocrysts of quartz and albite. 



The Tertiary lavas are grouped under the general names basalt, 

 andesite, and rhyolite. There is, however, considerable variety in the 

 rocks included undeT these names, as will be indicated in the special 

 descriptions. 



RH70LITE AND DACITE 



Under this head are included all the acid lavas, rhyolites, and dacites, 

 which when sufficiently crystalline usually contain free silica or quartz 

 and a variable amount of sanidine. There are large areas of rhyolite 



