682 



UNITED STATES MINERAL RESOURCES 



minerals apparently goes into the clay minerals that 

 are formed, but it remains in the 3-valent state or 

 oxidizes to the 4-valent state, both of which are rela- 

 tively insoluble. If erosion is insignificant but chemi- 

 cal leaching is intensive, the residual material may 

 be enriched in vanadium, as are some bauxites and 

 laterites, which commonly contain about 500 ppm V. 

 If, on the other hand, the clay minerals are removed 

 by erosion, most of the vanadium must stay with 

 these clay minerals during transport to places where 

 they accumulate as sedimentary rocks, for argilla- 

 ceous sediments commonly contain about as much 

 vanadium as do igneous rocks, whereas sandstones 

 contain only about 20 ppm V and limestones about 

 10 ppm. 



During the weathering of igneous, residual, or 

 sedimentary rocks, some vanadium oxidizes to the 

 5-valent state, especially in the intensive oxidizing 

 conditions of arid climates. In this state the vanadi- 

 um goes into surface or ground-water solutions and 

 remains in solution over a wide range of acidity and 

 alkalinity. It can be precipitated from solution and 

 locally concentrated in rocks under the following 

 three general conditions : 



1. By reaction with hydroxides of aluminum or 

 ferric iron. This process forms or enriches the va- 

 nadium concentration in some bauxites and residual 

 or sedimentary iron ores, some of which contain 

 about 500 ppm. 



2. By reaction with cations of heavy metals, such 

 as copper, lead, and zinc. This process forms the epi- 

 genetic vanadate minerals in the oxidized zones of 

 base-metal deposits. The vanadium concentrations 

 range from a trace to several thousand parts per 

 million V. 



3. By reduction in the presence of organic material 

 or biogenetically generated H2S. If the vanadium- 

 bearing solutions are moving through rocks, epi- 

 genetic ore deposits such as those in sandstone in 

 the Colorado Plateau region can be formed. On the 

 other hand, if the vanadium is carried to the seas by 

 surface waters, it can concentrate syngenetically in 

 phosphorites that are rich in organic material, and in 

 carbonaceous shales ; some of these shales contain as 

 much as 5,000 ppm V. Furthermore, if the organic 

 materials in these shales are converted to liquid 

 hydrocarbons, the vanadium can be moved as a dis- 

 solved constituent; some crude oils contain as much 

 as several hundred parts per million V. Vanadium ac- 

 cumulates in the ashes of these oils, and also in the 

 asphaltic residues resulting from natural or indus- 

 trial distillation of these oils, and these materials 

 have been used as commercial sources of vanadium. 



VANADIUM MINERALS 



Fischer and Ohl (1970) listed the names of 110 

 vanadium minerals, but only some 60 of these are 

 generally accepted by mineralogical authorities ; the 

 rest are considered to be inadequately described or 

 unneeded synonyms. Of the accepted vanadium min- 

 erals, most are scarce. The important ore minerals 

 are listed below; however, most of the vanadium 

 being produced currently is recovered from ores or 

 materials in which no specific vanadium ore mineral 

 is recognized. 



Carnotite: K2(UO.)2{V04)2«3HoO. A secondary mineral 

 in surface and near-surface deposits of vanadium and uran- 

 ium in sandstone; especially common in the Colorado Plateau 

 region. 



Coulsonite: (Fe,V)30i. A primary mineral exsolved from 

 magnetite in some titaniferous magnetite deposits; also with 

 magnetite in nontitaniferous magnetite deposits in Nevada. 



Descloizite-viottramite series : PbZn ( VOj) OH-PbCu 

 (VOj)OH. Includes araeoxene, chileite, cuprodesclozite, de- 

 chenite, eusynchite, psittacinite, ramirite, schaiTnerite, and 

 vanadite. Secondary minerals in the oxidized parts of base- 

 metal deposits; common in deposits in arid climates. 



Montroseite: (V,Fe)0*OH. A primary mineral, mostly in 

 deposits in sandstone; common but nowhere abundant. 



Patronite: VSi. A primary mineral in the asphaltite-vein 

 deposit at Mina Ragra, Peru. 



Roscoelite: Near K(V,Al)3Si30io(OH)2. A primary mineral, 

 common and abundant in vanadium deposits in sandstone, 

 sparse to moderate in some gold-quartz veins. 



Vanadinite: PbB(V0.i)3Cl. A secondary mineral in the 

 oxidized parts of some base-metal deposits. 



VANADIUM DEPOSITS 

 DEPOSITS OF MAGMATIC ORIGIN 

 TITANIFEROUS MAGNETITE DEPOSITS 



Vanadium-bearing titaniferous magnetite deposits 

 are associated with mafic and related igneous rocks, 

 most commonly anorthosite and gabbro. These rocks 

 occur in thick stratiform sheets or complex intrusive 

 bodies and are of deep-seated origin ; most of those 

 exposed are in continental shield areas and are of 

 Precambrian age ; only a few are younger. Magnetite 

 and ilmenite are the principal ore minerals, but some 

 hematite is present in some deposits. These minerals 

 occur in medium- to fine-grained intergrowths and 

 in exsolution and solid-solution relations. Small blebs 

 and exsolution blades of coulsonite have been recog- 

 nized in magnetite in a few deposits, but no vanadium 

 mineral has been identified in most deposits ; almost 

 always, however, vanadium is more abundant in the 

 magnetite (magnetic) concentrates of these deposits 

 than in the ilmenite concentrates. Ore grades in pro- 

 ductive deposits vary widely: 16-60 percent Fe, 1.5- 

 38 percent TiOj, and 0.1-2 percent V^O,. Small but 

 varied amounts of chromium, copper, and nickel oc- 

 cur in these deposits ; phosphorus is generally sparse. 



