Turner — Rocks and Minerals from California. 425 



dynamo-metamorphic form of the meta-augite-andesite tuff. 

 This contains layers of vein quartz, associated with which is 

 pyrophyllite in considerable masses crystallized in beautiful 

 stellate forms. The much decomposed and rusty schists in the 

 creek at the west base of the butte strike about 60° west of 

 north, and dip at an angle of 80°. At one point about due 

 west of the butte the schists are covered with an efflorescence. 

 Some of this was collected and examined by Dr. H. N. Stokes 

 in the laboratory of the U. S. Geological Survey, who reported 

 that the efflorescence is composed of hyclrated sodium and 

 magnesium sulphates with a little chloride. In the interior of 

 this efflorescence are grains of calcium sulphate. 



The quartzite-like rock under the microscope is seen to be 

 made up chiefly of grains of quartz and a positive uniaxial 

 mineral of greater relief than the quartz, extinguishing parallel 

 to the cleavage and having bright interference colors. Dr. 

 Hillebrand made a chemical examination of this rock and came 

 to the conclusion that the unknown mineral might be alunite. 



Chemical Analysis of Alunite No. 870 S. N. 



Si0 2 2-64 



Ti0 2 ._._ -40 



A1 2 G 3 38-05 



Fe 2 3 -23 



FeO Not looked for 



MnO None 



CaO -55 



BaO Not looked for 



MgO trace 



K 2 4-48 



Na 2 2-78 



P 2 5 trace 



C0 none 



H 2 100°- none 



H a O 100°+ 11-92 



S0 3 38-50 



99*55 

 To make this more certain a quantity of the rock was pow- 

 dered and the alunite-like mineral separated by means of the 

 Thoulet solution. The specific gravity of the mineral is 2'78 

 as determined with the Westphal balance by grains suspended 

 in Thoulet solution. Some of the material was heavier than 

 this, but this greater specific gravity was undoubtedly due to 

 inclusions of a brownish red mineral in minute grains without 

 crystal outlines. These grains are too minute for satisfactory 

 determination with the microscope, but a quantitative test of 

 some that were separated from the rock, made by Mr. William 

 Yalentine, show that the mineral is rich in titanium. The 

 mineral does not resemble titanite in color, at least such titanite 



