University of California . 



[W.L. I. 



of this feldspar to quartz, in its water-clear character and freedom 

 from cleavage and twinning, leads to a chemical investigation for 

 final discrimination. Fragments tested by Szabo's method of flame 

 tests gave uniformly strong reactions for sodium, and corresponded 

 generally to albite. A portion was freed from amphibole by means 

 of the methylene iodide solution, and found to have a specific gravity 

 of 2.634. A partial analysis of the material thus separated yielded 



figures which, taken together with the facts before presented, prove 

 conclusively that the ground mass is a very pure albite unmixed 

 with quartz. 



The feldspar contains numerous inclusions, both liquid and 

 solid. The liquid inclusions are round or angular in form, gen- 

 erally contain bubbles which are sometimes in rapid motion, and 

 are arranged in bands or zones extending from grain to grain, or 

 more frequently are scattered quite irregularly through the feldspar 

 substance. The solid inclusions consist of minute grains and needles 

 of the blue amphibole, grains of magnetite, crystals of zircon, and 

 grains of sphene or titanite. The zircon is distinguished by its 

 characteristic crystal form, high relief, brilliant polarization colors, 

 and parallel extinction. The sphene never shows crystal outlines, 

 but is in irregular grains or granular aggregates, sometimes reaching 

 a diameter of 1 mm., and is very abundant in the rock. It is the 

 material of the yellow specks mentioned before as visible macro- 

 scopically. It is colorless or yellowish gray in thin section, with 

 irregular cracks and rarely sharp cleavages, which are generally 

 bordered by a dark gray decomposition product. It exhibits high 

 relief, strong double refraction, and very brightly colored biaxial 

 interference figures. A few grains separated in the heavy solution 

 gave a specific gravity of 3.49, and their solution in sulphuric acid 

 gave a strong reaction for TiO,, with hydrogen peroxide. 



Secondary Veins. — The veins of greenish color appear in thin 

 section as aggregates of large feldspar grains, most of which are 

 simple albite twins, with extinction angles on M of about 16°. The 



SiO, 



A 1,0, 

 CaO 







o 



