Zircon and Baddeleyite

Normally, zircon sand is readily available as a by-product of mtile and ilmenite mining at ca 150 per metric ton. However, zircon and baddeleyite are obtained as by-products of their operations, and therefore, the supply is limited by the demand for other minerals. In 1974, when a use for zircon in tundish nozzles developed in the Japanese steel industry, a resulting surge in demand and stockpiling raised zircon prices to 500/t. Worldwide production by country is given in Reference 80. 

Further applications of LA-MC-ICP-MS using the Plasma 54 by Zr isotope ratio measurements in zircon and baddeleyite samples are described by Hirata.147 The isotope ratios 92Zr/90Zr = 0.333 94 0.000 02 and 96Zr/90Zr = 0.054 63 0.000 01 have been determined on a Merck reagent with a precision of 0.01-0.02% and 0.03-0.04%, respectively. Neither isotopic variation in the... 

Zr/94Zr isotope ratio (due to the radiogenic contribution of 92Nb) nor isotopic heterogeneity was found for any of the investigated zircon and baddeleyite samples. 

It has been recognized that the Lu-Hf isotopic system in zircon is a powerful tool for deciphering the evolution of the earth s crust and mantle. " Zircon normally contains 0.5-2 wt % Hf, which results in an extremely low Lu/Hf ratio (" Lu/" Hf < 0.002) and consequently a negligible radiogenic growth of Hf due to the decay of Lu. Therefore, the Hf/" Hf ratio of zircon can be regarded as the initial value at the time when it crystaUized. LA-ICP-MS with a multiple ion collector system has also been employed to study the hafnium isotopic composition of zircon and baddeleyite standards in U-Pb geochronology. °°... 

Hafnium is always found with ores of zirconium in the earth. The most common of those ores are zircon and baddeleyite. 

Wingate, M. T. D. 2000. Ion microprobe U-Pb zircon and baddeleyite ages for the Great Dyke and its satellite dykes, Zimbabwe. South African Journal of Geology - Suid-Afrikaanse Tydskrif vir Geologic, 103, 74-80. 

The most important zirconium minerals are zircon and baddeleyite, often associated with rutile and ilmenite deposits. Zircon and baddeleyite are characterized by strong luminescence under powerful laser excitation. The main background emission is connected with organic matter sorption and sometimes with fluorite. Emission spectra of zircon and baddeleyite together with their decay times demonstrate that delay time of 200 ns and gate of 10-50 ps combined with excitation near 300 nm enable to remove background signal drastically. 

Baddeleyite, a naturally occurring zirconium oxide, has been found in the Poco de Caldas region of the states of Sao Paulo and Minas Geraes in Brazil, the Kola Peninsula of the former USSR, and the northeastern Transvaal of the Repubflc of South Africa. BraziUan baddeleyite occurs frequently with zircon, and ore shipments are reported to contain 65—85% zirconium oxide, 12—18% siUca, and 0.5% uranium oxide. Veryhttle of this ore is exported now because all radioactive minerals are under close control of the BraziUan government. 

Mixed zircon, coke, iron oxide, and lime reduced together produce zirconium ferrosiUcon [71503-20-3] 15 wt % Zr, which is an alloy agent. Fused zirconia [1314-23-4] has been made from zircon but baddeleyite is now the preferred feed for the production of fused zirconia and fused alumina—zirconia by electric-arc-fumace processing. 

Occurrence. The more important minerals are zircon (ZrSi04) and baddeleyite (a form of Zr02). 

Hafnium was discovered in 1922 by Coster and deHevesy. They named it for Hafnia, the Latin word for Copenhagen. It is found in aU zirconium ores, such as zircon, (ZrSi04) and baddeleyite (Zr02). It occurs in the earth s crust at about 3 mg/kg. Its average concentration in sea water is 7 ng/L. 

Zirconium is found in small amounts widely spread throughout nature, occurring in many alluvial deposits of lake and stream beds and ocean beaches. The most important mineral is zircon, or zircon orthosilicate, ZrSi04. Other zirconium minerals are eudialite, (Na, Ca, FeleZrSieOislOH, Cl), and baddeleyite, Zr02. It also occurs in monazite sand. The abundance of zirconium in the earth s crust is estimated as 165 mg/kg. 

Zirconium comprises 0.016% (162 ppm) of the Earth s crast and, as a transition element, is only less abundant than Fe, Ti, and Mu. Hafnium is much less abundant at 2.8 ppm, but is stUl comparable in quantity to Cs and Br. The most important minerals of zirconium are zircon (ZrSi04), which is mostly mined in Australia, South Africa, the USA, and Sri Lanka, and baddeleyite (Z1O2), found mostly in Brazil. The estimated reserves exceed a billion tonnes. Australia and South Africa account for about 80% of zircon mining. All zirconium minerals are contaminated by small quantities of hafnium (0.5-2% of Zr content), but in a few (such as alvite, MSi04 XH2O, M = Hf, Zr, Th) the content of Hf is comparable with that of Zr. The above-mentioned similarities in the chemical behavior of these metals explain their close association in Nature and the similarity of their isolation procedures. 

The names of these ores are used loosely, especially in commercial circles. Baddeleyite is Zr(V, brazilite is the Brazilian dioxide, mixed with varying amounts of zirkelite, which is (CaFe)O- 2(ZrTiTh)Ov zircon, and a nsw unnamed silicate. The term zirkite is a trade name, applied to the partially purified Ore this name does not appear in the 1922 edition of Dana s Mineralogy. 

The abundance of hafnium in the Earth s crustal rocks is 2.8 mg kg and is comparable with that of Cs and Br. Hafnium is found in minerals of zirconium, such as zircon (ZrSi04) and baddeleyite (Zr02). 

An altered zircon, cyrtolite, which is a hydrated zirconium silicate in which part of the zirconium is replaced by hafnium, and divalent and trivalent metals, is used as the raw material. This ore, although not very abundant, is used as the source material rather than the zircon or baddeleyite (1) because of its higher hafnium content (5 to 9 per cent compared to 2 per cent or less for the normal ores), and (2) because it is easily susceptible to acid attack. Ordinarily silicates are not easily attacked by acid treatment and must be handled by some fusion method. However, Urbain reported successful extraction by sulfuric acid at 65° of malacon, an altered zircon, and other investigators have noted that cyrtolite also yields to sulfuric acid treatment. 

Hafnium is more abundant than uranium and tin in the Earth s crust, with 5.3 ppm wL As previously discussed, the close chemical similarity between hafnium and zirconium leads to their parallel association in natural ores and minerals where hafnium is invariably found in zirconium ores in quantities of between 1 and 2 wL%. Apart from specific zirconium ores such as zircon or baddeleyite where hafnium is always present, chief and specific hafnium-bearing minerals are rare the nesosilicates Ho/hon [HfSiOJ and Alvite [(Hf, Zr, ThlSiO xH O]. 

Mine production Zircon Reserves and baddeleyite (thousand metric tons)... 

Non-refractory primary uranium minerals are rare, but uranothorianite has been reported from Palabora" and uraninite from Lake Nipissing, Ontario, Canada. Most car-bonatite uranium-bearing minerals me refractory phases. Uranium occurs as a minor or trace element in zircon, apatite, baddeleyite, perovskite, monazite, pyrochlore minerals, goyazite, bastnaesite, allanite, anatase, rutile, etc. The secondary mineral autunite occurs in soil covering the Araxa carbonatite. " ... 

As these zircons were discordant and baddeleyite reversely discordant, it is unfortunately not possible to assess whether the zircon normalization gave the correct U-Pb ages for baddeleyite. 

The manufacture of zirconium metal is similar to that of titanium The raw materials zircon (ZrSi04) and baddeleyite (Zr02-containing ore) are processed by chlorination with coke as a reducing agent... 

There are several crystal-structural modifications of zirconium oxide (Zr02), analogues of the minerals arkelite and baddeleyite the latter of these is the form normally encountered as a pigment. Blumenthal and Jacobs (1973) indicate that there were two production methods. The first involves heating zircon (. v.) and carbon at temperatures in excess of 2000°C to form zirconium carbide this would then be burnt in air to form zirconium oxide. In the second process, zirconium salts were precipitated with an alkali sulfate this apparently gives very pure polysulfatopolyzir-conic acids , calcination of which yields the pure oxide. 

Zirconium occurs naturally as a siUcate in zircon [1490-68-2] the oxide baddeleyite [12036-23-6] and in other oxide compounds. Zircon is an almost ubiquitous mineral, occurring ia granular limestone, gneiss, syenite, granite, sandstone, and many other minerals, albeit in small proportion, so that zircon is widely distributed in the earth s cmst. The average concentration of zirconium ia the earth s cmst is estimated at 220 ppm, about the same abundance as barium (250 ppm) and chromium (200 ppm) (2). 

Zirconium is found in at least 37 different mineral forms (6) but the predorninant commercial source is the mineral zircon, zirconium orthosiUcate. Other current mineral sources are baddeleyite and eudialyte [12173-26-1]. 

It is found in the ores baddeleyite (also known as zirconia) and in the oxides of zircons, elpidite, and eudialyte. 

Zirconium oxide occurs in nature as mineral baddeleyite. Ore is mined from natural deposits and subjected to concentration and purifcation by various processes. The oxide, however, is more commonly obtained as an intermediate in recovering zirconium from zircon, ZrSi04 (See Zirconium, Recovery). 

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