Zircon, zirconium

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]. 

The best sealed-in minerals are zircons, zirconium silicate minerals which are formed when melted lava on the flanks of volcanoes solidifies. When the zircons crystallize out, they incorporate radioactive uranium (in particular 238U), which decays in several steps, leading Anally to the lead isotope 208Pb. The rate of decay is very low, as the half-life of uranium-238 is 4.5 x 109 years. Thus, the U-Pb-zircon method for age determination of Precambrian rock is very important. The fossils studied by Schopf were sandwiched between two lava layers (Schopf, 1999). The volcanic layers were dated to 3.458 0.0019 x 109 years and 3.471 0.005 x 109 years the age of the fossil layer (Apex chert) was thus determined to be about 3.465xlO9 years. 

Zirconia. Zircon (zirconium silicate), the most widely occurring zirconium-bearing mineral, is dispersed in various igneous rocks and in zircon sands. The main deposits are in New South Wales, Australia Travancore, India and Florida in the United States. Zircon can be used as such in zircon refractories or as a raw material to produce zirconia. The zircon structure becomes unstable after about 1650°C, depending on its purity, and decomposes into Zr02 and Si02 rather than melting (see Zirconiumand zirconium compounds). 

Zirconia. Zircon (zirconium silicate), the most widely occurring zirconium-bearing mineral, is dispersed in various igneous rocks and in zircon sands, Zircon can be used as such in zircon refractories or as a raw material to produce zirconia, ZrC>2. 

Another example is found in the analysis of the mineral zircon. We had previously published [4] a spectrum of a positive ion laser desorption spectrum of a sample of the mineral zircon (zirconium silicate) showing uranium as 238U+, present in the sample at a level of approximately 15 parts-per-million [41]. The spectrum, which showed mixed zirconium oxides and hydroxides as the most intense peaks in the spectrum, was taken with a four second delay between the laser pulse and ion detection, in order to allow neutrals to be pumped out of the cell. These conditions had been found adequate for analysis of organic compounds. However, it was found that the reactivity of zirconium was such that the mixed oxides and hydroxides were produced as ion-molecule reaction products during the long trap period. 

About 95 percent of all zirconium produced is converted into a compound before being used. The two most common compounds made are zircon (zirconium silicate) and zirconia (zirconium oxide). 

There are a number of ways of obtaining U-Pb ages on zircons, but in the last two decades the use of the ion microprobe has become the method of choice. Zircon (zirconium silicate, ZrSi04) is a common mineral in granitic rocks, often abundant as a detrital mineral in clastic sediments and a rare accessory mineral in mafic rocks and some metamorphic rocks. The frequent occurrence of the mineral zircon, and its resilience to later thermal events that would reset other isotopic systems are the reasons for its frequent use in studies of the early Earth. 

The given material is characterized not only by chemical, but also by phase heterogeneity. The various phases have unequal reaction ability, i. e., during the synthesis of ceramics the preservation of the unreacted free phases of plutonium is rather probable. To increase the reaction ability of the precursor, it was offered to use an additive of surplus quantity of metal zirconium powder with a subsequent synthesis of polyphase ceramics on the basis of zircon/zirconium dioxide (Zr,Pu)Si04/(Zr,Pu)02, as well as other phases of non-radioactive elements -impurities. 

Synonyms Hyacinth Silicic acid, zirconium salt (1 1) Silicic acid, zirconium (4+) salt (1 1) Zircon Zirconium orthosilicate Zirconium (IV) silicate (1 1)... 

Most commercial thorium is extracted from monazite, which is not amenable to breakdown by dilute acids. Thorite, or thorium silicate, is an alternative thorium ore which occurs in fairly large quantities in some parts of the world, for example in the tailings from the tin beneficiation processes in Nigeria. The ore contains principally zircon (zirconium silicate), but this is of much smaller value than the 5 to 10 per cent thorite content. 

The metal zirconium is not as rare as might be expected. It is eighteenth in abundance in the earth s crust and more common than copper and zinc together. The most important mineral is zircon, zirconium silicate ZrSiO. Badddeyite, zirconium oxide ZrOj (Table 19.1) is also important There are, however, no zircon mines. Zircon is recovered as a by-product from the extraction of titanium from ores containing the minerals rutile and ilmenite. 

---