350 University of California Publications. [Geology 



The chemical analysis was kindly undertaken by Professor 

 Blasdale. A and B were made on the blue material and C on 

 the white 





A. 



B. 



Ay. 



Mol. Batios. 



C. 



SiO, 



43.56 



43.79 



43.68 



.723 



43.61 



Ti0 2 



20.18 



20.00 



20.09 



.250 



19.50 



BaO 



36.34 



36.31 



36.33 



.237 



37.01 





100.08 



100.10 







100.12 



From these is derived the formula BaTiSi.,0,, which yields 



the following' calculated values. 



Si0 2 43.71 

 Ti0 2 19.32 

 BaO 36.97 



In an attempt to account for the color of the mineral Bias- 

 dale made various qualitative tests, and reports: "A more 

 careful examination of a two-gram portion of the blue mineral 

 failed to show the presence of appreciable amounts of iron, cobalt, 

 manganese, copper or chromium. Very minute quantities of 

 sodium and aluminum were obtained, but the amounts were so 

 small as to render it probable that they were derived from the 

 action of the reagents on the glass vessels employed rather than 

 from the mineral itself. Conclusive evidence of the presence of 

 the rarer earths, especially zirconium, tantalum and columbium, 

 could not be obtained. Careful examination of some of the 

 mineral in a delicate electroscope gave no indications of radio- 

 activity." "It was also shown that all the titanium was present 

 in the higher degree of oxidation. On dissolving the mineral in 

 hydrofluoric acid in an atmosphere of carbon dioxide a colorless 

 solution was obtained which failed to reduce potassium perman- 

 ganate. ' ' 



Benitoite is considered by both of us a very acid titano- 

 silieate. Blasdale notes that the formation of salts of an 

 extremely acidic character is not unusual when the acid con- 

 cerned possesses very weakly acidic properties and the base very 

 strongly basic ones, also that silicon dioxide possesses a remark- 

 able tendency for the formation of complex poly-acids and that 

 it is not improbable that the very closely related titanium 

 dioxide might partially replace it atom for atom in such a com- 

 pound as the mineral under consideration. He suggests that the 



