Zirconium-bearing minerals

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. 

NRC has issued an assessment of potential doses to the public associated with the distribution, use, and disposal of exempt products or materials containing low levels of source or byproduct material (Schneider et al., 2001) (see Section 4.1.2.5.2). In a case involving disposal of large volumes of zircon sand produced in processing of zirconium-bearing minerals, the estimated annual dose to a future on-site resident at a disposal site was 100 p.Sv, due to the elevated levels of thorium and uranium. In all other cases, however, the estimated annual dose was substantially less than 10 xSv. Since the volumes of exempt material were large in many cases, this analysis indicates that substantial volumes of waste that contains low levels of radionuclides are potentially exemptible. 

Sabinaite, a new anhydrous zirconium bearing carbonate mineral from Montreal Island, Quebec. 1681 ... 

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]. 

With a relative abundance in the Earth s crust of 122 mg/kg, chromium is the 21st most abundant element and the 6th most abundant transition metal after iron, titanium, manganese, zirconium, and vanadium it is more abundant than nickel, zinc, and copper. Though native chromium is extremely rare (e.g, Udachnaya Mine in Russia), most common chromium-bearing minerals are the spinel-type mineral chromite [FeCr O, cubic] and, to a lesser... 

Hafnium is dispersed in the Earth s crust to the extent of three parts per million, and is invariably found in minerals of zirconium up to a few percent compared with zirconium. Hafnium vapor has been identified in the Sun s atmosphere. Commercial sources of hafnium-bearing zirconium minerals are found in beach sands and river gravel in the United States (principally Florida), Australia, Brazil, western Africa, and India. Hafnium is concentrated in the upper horizons in a weathering profile of gabbroic rocks (Serpa, Portugal) ranging between 1.0 and... 

Sodium tetraborate or combinations of boric acid, boric oxide, or sodium tetraborate with sodium carbonate have been used to decompose aluminosilicates and refractory minerals such as zirconium or chromium-bearing ores. Pt crucibles are used and dilute hydrochloric acid is used for leaching the melt. 

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