212 Ilillehrand — Vanadium and Molybdenum in Rocks. 



21 a shows, however, practically the same amount as its mother 

 rock, the syenitic lamprophyre 21. 



In most of these cases, notably the last one, the vanadium in 

 the separated mineral is not sufficiently in excess of that in the 

 rock from which it was taken to account for all of that found 

 in the latter. Hence, if the determinations are correct it must 

 also be a constituent of some other mineral than the one 

 analyzed. In roscoelite the trivalent condition of vanadium 

 corresponding to the oxide V 2 3 is now recognized as probable, 

 although Roscoe's analysis reports V 2 B and Genth's an oxide 

 intermediate between Y 2 3 and V 2 5 . This assumption seems 

 to be necessary if the mineral is to be regarded as a mica, and 

 it is then doubtless the equivalent of trivalent iron or alumi- 

 num. It would then be natural to look for it in the alumi- 

 nous or ferric silicates of igneous rocks, certain biotites, pyrox- 

 enes, and hornblendes, and its absence in such minerals as ser- 

 pentine and chrysolite, as shown by analyses 3 and 60, appears 

 natural enough. 



Few and inconclusive as the above comparisons are, they 

 seem to favor strong^ this view as to the source of the vana- 

 dium and in a measure are confirmatory of the observation of 

 Hayes. (Proc. Am. Ac, x, 294, 1875), who rather indefinitely 

 associates it with phosphorus and proto-salts of iron and man- 

 ganese, which are usually more prominent components of 

 basic than of acid rocks. 



We are probably justified by the evidence in tabulating the 

 vanadium as V 2 3 in analyses of igneous and some meta- 

 morphic rocks which have undergone little or no oxidation, 

 but with sandstones, clays, limestones, etc., which are of more 

 or less decided secondary origin, this is probably not the case. 

 The probabilities are there largely in favor of its acid character 

 and the existence of various vanadates of calcium, iron, 

 aluminum, etc., in which case it should appear in analytical 

 tables as V" 2 5 .* 



It was not until the greater part of the above tests had been 

 finished that any careful attempt was made to identify molyb- 

 denum as well as vanadium. From the evidence gathered 

 during the later part of the work it would seem that molyb- 

 denum when it does occur is a much less important constituent 

 quantitatively than vanadium, and that unlike the latter it 

 accompanies the more acid rocks. Molybdenite is a well 

 known accessory constituent of some granites, etc., but in the 

 above instances its amount was extremely small and no hint 

 was obtained as to its state of combination. 



* In the regular course of analysis vanadium will be weighed with alumina, 

 iron, titanium, etc., since it is precipitated by both ammonia and sodium acetate 

 in presence of those and other metals, hence the alumina percentages in 



