VANADIUM 



683 



The ore minerals crystallized with the silicate min- 

 erals from the magma, and commonly they occur 

 disseminated in large masses of rock or were segre- 

 gated by crystal settling into extensive lenses or 

 layers as much as several feet thick. Some bodies of 

 magnetite and ilmenite occur as plugs, dikes, and 

 irregularly shaped masses that presumably were 

 injected into these forms when conditions caused 

 remelting of these minerals in places where they 

 originally crystallized. Deposits vary widely in size 

 — from those too small to be mined to those that con- 

 sist of several billion tons of ore containing several 

 million tons of vanadium. 



NONTITANIFEROUS MAGNETITE DEPOSITS 



Nontitaniferous magnetite deposits, by arbitrary 

 definition, contain less than about 1 percent TiOo. 

 They also generally contain less vanadium but more 

 phosphorus than do the titaniferous magnetite de- 

 posits — commonly 0.1 to about 0.5 percent V2O5 and 

 more than 0.1 percent P. Their geologic habits are 

 less consistent than those of the titaniferous magne- 

 tite deposits; some of them are derived from mafic 

 igneous rocks but others are associated with igneous 

 rocks of intermediate or syenitic composition, and 

 some deposits are apparently wholly magmatic 

 whereas others have the characteristics of contact 

 or hydrothermal replacement bodies. Magnetite, the 

 principal ore mineral in these deposits, occurs in dis- 

 seminated or massive bodies ; the iron content ranges 

 from about 30 to 60 percent Fe. Apatite is present in 

 the deposits rich in phosphorus. 



VANADIUM-BEARING HYDROTHERMAL VEIN DEPOSITS 



Vanadium is sparse in typical hydrothermal vein 

 deposits except those containing titanium minerals 

 and some containing gold. A few tenths percent V2O5 

 is common in the titanium minerals ilmenite, rutile, 

 and brookite, and also in the uranium-titanium-iron 

 mineral davidite, where these minerals occur in 

 veins. Nolanite (Fe4Vxo023, Fe^VgOis) is intergrown 

 with ilmenite and other vein minerals in the urani- 

 um-bearing veins in the Goldfields district, Sas- 

 katchewan, Canada (Robinson, 1955). In some gold- 

 quartz veins, especially those containing gold- 

 telluride minerals, roscoelite, the vanadium-bearing 

 mica, is conspicuous. The roscoelite is finely inter- 

 grown with quartz and other gangue minerals, and 

 in places it forms small aggregates along the vein 

 walls. The vanadium content of these veins is as- 

 sumed to be low, although no grade data have been 

 found except for the Kekionga-Magnolia vein. Mag- 

 nolia district, Colorado, where "a moderate tonnage 

 averaging 2 percent vanadium oxide was blocked 

 out" (Lovering and Goddard, 1950, p. 234). 



EPIGENETIC DEPOSITS 

 VANADATE DEPOSITS 



Vanadates of lead, zinc, and copper (vanadinite 

 and minerals of the descloizite-mottramite series) 

 are common in the oxidized zones of base-metal 

 deposits, especially in areas of arid climate and deep 

 oxidation. These minerals form crusts and partly fill 

 cavities in the altered and leached material of the 

 primary base-metal sulfide veins and replacement 

 bodies. The vanadate ore bodies are irregular in 

 shape and varied in size and grade ; most are rather 

 small and low in grade. Carbonate rocks are the host 

 to most deposits, but some deposits are in silicic 

 igneous rocks. It is generally assumed that the va- 

 nadium was introduced by oxidizing ground waters 

 from remote sources because the vanadium contents 

 of the primary sulfide deposits and the country rocks 

 are virtually nil. 



DEPOSITS IN SANDSTONE 



Vanadium deposits in sandstone have been the 

 principal source of this metal until recent years; 

 similar but unimportant deposits are known in lime- 

 stone and shaly sandstone. Typically, the productive 

 deposits occur in stream-laid sandstone lenses sev- 

 eral tens of feet thick and 1 mile to several miles 

 wide, interbedded with mudstone of flood-^plain or 

 lacustrine origin. These beds accumulated on broad 

 alluvial plains or fans, and all are of late Paleozoic 

 age or younger, probably coincident with the evolu- 

 tionary development of land plants; coalified fossil 

 plant material is present in most deposits. A few 

 productive deposits are in beds of clean sandstone of 

 eolian origin. 



Varied amounts of uranium and copper are as- 

 sociated with vanadium in these deposits. The prin- 

 cipal primary ore minerals are silicates and oxides of 

 both vanadium (mainly roscoelite and montroseite) 

 and uranium (coffinite and uraninite) and the com- 

 mon sulfides of copper; carnotite is the principal 

 secondary vanadium-uranium mineral. These min- 

 erals chiefly fill the pores of the sandstone, but they 

 also partly replace the sand grains and the plant 

 fossils. Ore grades are commonly 1-2 percent V2O5, 

 0.05-0.25 percent UsOs, and a trace to 1 percent Cu. 

 Some ore bodies are irregular in shape, but most of 

 them are tabular; they average only a few feet in 

 thickness and lie nearly parallel to the bedding of the 

 host rock. Ore bodies range in size from a few tons 

 of ore to more than a million tons. Individual de- 

 posits are discrete bodies and are separated from 

 neighboring deposits by barren sandstone ; neverthe- 

 less, deposits tend to be clustered in patches of 

 ground a few miles across and to recur in a favored 



