Mineral wolframite

Scandium is apparently much more abundant (the 23rd most) in the sun and certain stars than on earth (the 50th most abundant). It is widely distributed on earth, occurring in very minute quantities in over 800 mineral species. The blue color of beryl (aquamarine variety) is said to be due to scandium. It occurs as a principal component in the rare mineral thortveihte, found in Scandinavia and Malagasy. It is also found in the residues remaining after the extrachon of tungsten from Zinnwald wolframite, and in wiikite and bazzite. 

Nearly all transition metals are oxidized readily, so most ores are compounds in which the metals have positive oxidation numbers. Examples include oxides (Ti02, mtile Fc2 O3, hematite C112 O, cuprite), sulfides (ZnS, sphalerite M0S2, molybdenite), phosphates (CeP04, monazite YPO4, xenotime both found mixed with other rare earth metal phosphates), and carbonates (FeC03, siderite). Other minerals contain oxoanions (MnW04, wolframite) and even more complex stmctures such as camotite, K2 (002)2 ( 4)2 2 O ... 

The electrostatic separation method is the exclusive choice in some specific situations, for example in the cases of rutile and ilmenite deposits. These deposits generally contain minerals of similar specific gravities and similar surface properties so that processes such as flotation are unsuitable for concentration. The major application of electrostatic separation is in the processing of beach sands and alluvial deposits containing titanium minerals. Almost all the beach sand plants in the world use electrostatic separation to separate rutile and ilmenite from zircon and monazite. In this context the flowsheet given later (see Figure 2.35 A) may be referred to. Electrostatic separation is also used with regard to a number of other minerals. Some reported commercial separations include those of cassiterite from scheelite, wolframite from quartz, cassiterite from columbite, feldspar from quartz and mica, and diamond from heavy associated minerals. Electrostatic separation is also used in industrial waste recovery. 

Ta/Nb minerals often occur as impurities in ilmenite, rutile, cassiterite, wolframite and perovskite, most of which contain REE. Because tantalite and columbite have similar chemical properties, they often replace each other, and are usually found as isomorph mixtures. Tantalum and niobium can also be found as separate minerals. Tantalite and microlite are primary sources of tantalum. 

Tungsten (W, [Xe]4/145d46s2), name after the Swedish tung sten (heavy stone), symbol after the name of mineral wolframite (from which it was originally isolated). The name wolfram is still used mainly in the German literature. Isolated (1783) by Spanish chemists Juan Jose and Fausto d Elhuyar. 

ORIGIN OF NAME Tungsten was originally named "Wolfram" by German scientists, after the mineral in which it was found, Wolframite—thus, its symbol "W." Later, Swedish scientists named it tung sten, which means "heavy stone," but it retained its original symbol of "W."... 

In the mid-1700s a number of scientists experimented with and attempted to isolate element 74 by treating ores of other metals with reagents. One problem was that tungsten was often confused with tin and arsenic. It was not until 1783 that Don Fausto de Elhuyar (1755-1833) and his brother Don Juan Jose de Elhuyar isolated a substance from tin ore that they called wolframite. They named it after the mineral in which it was found. At about the same time the Swedish named it tung sten, which means heavy stone in Swedish. This explains the potentially confusing use of W for the symbol for tungsten. 

Anomalous values of Au, Cu, Sn, Bi, As, and W in the Psi indicate the precipitation of high temperatures minerals and metals that are represented by a complex mineralogy. The correlation between Ag-Pb-Bi-Sb suggests the presence of different Ag-Pb-Bi sulfosalts correlation between Ag-Cu-Sb is associated with freibergite, argentotenantite, and tetrahedrite, while Sn-W is related to wolframite and cassiterite, and In-Sn-Sb with ferrokesterite, stannite and cassiterite. In Ps2 the In and Cd, are present in the Fe-rich sphalerite (Crespi 2006) showing a high correlation between In-Zn-Cd the correlation between In-Sn is associated with ferrokesterite. The presence of Ag-Pb sulfosalts is... 

Scadium occurs in nature, very widely dispersed in low concentrations. It is found in most soils and numerous minerals in very minute quantities. The principal minerals are wolframite, euxenite, wiikite, bazzite, cassiterite, gadolinite, and throtveitite. Its abundance in the earth s crust is estimated to be 22 mg/kg. The element also has been detected in the sun and other stars. 

Tungsten is recovered mostly from mineral scheebte and wolframite. The recovery process depends on the mineral, the cost, and the end use i.e., the commercial products to be made. Typical industrial processes have been developed to convert tungsten ores to tungsten metal and alloy products, tungsten steel, non-ferrous alloys, cast and cemented tungsten carbides, and tungsten compounds. A few processes are mentioned briefly below. 

If tungsten is recovered from the wolframite group mineral, the wolframite concentrate is boiled or pressure-digested with 50% caustic soda solution. Alternatively, they may be fused or sintered with caustic soda, caustic potash or sodium carbonate and the fused mass then leached with water. The solution is filtered to separate sodium tungstate solution. The fdtrate is subjected to various treatments to remove molybdenum, phosphorus, and arsenic impurities. The filtrate at this point is essentially a solution of sodium tungstate and is treated in the same way as that obtained from the scheehte concentrate discussed above. 

Tungstic acid is obtained as an intermediate in the recovery of tungsten from its minerals, scheebte and wolframite (See Tungsten). Also, the tungstic acid may be prepared by heating sodium tungstate with sulfuric acid or hydrochloric acid ... 

In the meantime two Spanish chemists, the de Elhuyar brothers, discovered in wolfram, a dark brown mineral (wolframite) then supposed to be an ore of tin and iron, an acid (wolframic) which they found to be identical with tungstic acid (2, 21, 25, 37, 38). 

While the blendes contain indium as the sulfide, continued Winkler, Hoppe-Seyler found it in another form, which could not be definitely determined, in a tungsten ore from an unknown locality, and later in the wolframite from Zinnwald. The latter contains 0.0228 per cent of indium. In the meantime, I have placed many minerals (without previous concentration, to be sure) before the slit of the spectroscope, but have never found one which gave the desired reaction. It therefore seems as if the occurrence of indium in nature is exceedingly scarce or it must in most cases play the role of a difficultly discoverable satellite (81). 

In mineralogy, a linear relation between hardness and chemical composition is common, applying specifically to all series of isomorphous minerals, such as Au-Ag (Fig. 5.16a), plagioclases, ferberite-wolframite-hibnerite,... 

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