216 Ilillebrand — Vanadium and Molybdenum in Rocks. 



Summary of Results. 



Vanadium occurs in quite appreciable amounts in the more 

 basic igneous and metamorphic rocks, up to *08 per cent or 

 more of V 2 3 , but seems to be absent or nearly so from the 

 highly siliceous ones. The limited evidence thus far obtained 

 points to the heavy ferric-aluminous silicates as its source — the 

 biotites, pyroxenes, amphiboles. As opportunities offer fur- 

 ther evidence will be accumulated and it is hoped that other 

 chemists will lend their aid. 



Limestones and sandstones appear to contain very small 

 amounts of vanadium, as shown by analyses of a composite 

 sample of each aggregating over 700 different occurrences. 



From the few tests for molybdenum it appears as if this 

 element were confined to the more siliceous rocks. It is pres- 

 ent in no observed case in amount sufficient for quantitative 

 measurement when operating on five grams of material. 



Laboratory of the U. S. Geological Survey, 

 Washington, D. C, May 1898. 



Note. Since the above was written a few tests have been 

 made on minerals of which powdered samples were at hand. 

 A phlogopite from Burgess, Canada, gave *007 per cent V 2 O s . 

 Mica from Laurel Hill, Georgia, gave '026 per cent V 2 8 . Pro- 

 tovermiculite from Magnet Cove, Ark., gave '04 per cent V a O s . 

 Hallite from Chester Co., Pa., gave *0l percent V 2 3 . Jeffer- 

 sonite from Franklin, N. J., gave none, and a non-ferruginous 

 amphibole from St. Lawrence County, N. Y., gave a faint 

 trace. 



