Zirconium silicate zircon

The data, in the temperature range 53 to 1173 K, has been re-interpreted in this review. The temperature dependence of the heat capacity, as determined by least squares analysis, is given by  

The selected heat capacity at 298.15 K determined from the least squares regression is  

This value is in very good agreement with that seleeted by Robie and Hemingway [95ROB/HEM] (98.64 J-K -mol ) in their eompilation of the thermodynamie properties of minerals and related substances. 

The heat capacity equation (V.81) was used to derive an expression for the entropy change in the temperature range 53 to 1173 K. Below 50 K, Kelley [41KEL] extrapolated a value for the entropy change of 2.34 J-K -mor from the funetion sum (using Debye and Einstein terms) derived between 51 and 298 K the Einstein terms, however, only contribute a negligible amount to the value. The values obtained below and above 50 K were then combined to derive a value for the standard entropy at 

This selected value is in excellent agreement with that determined by [41KEL] (84.1 J-K -mor ) and the value selected by [95ROB/HEM] (84.0 J-K -mor ). 

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Zircon pigments are derived from the tetragonal zirconium silicate, ZrSi(>4. Because uf Lite high temperature (up to 1600°C) and chemical stability of zirconium silicate, zircon pigments can be used in the formulations of high temperature (1300- 14O0cC) glazes, Zirconium silicate is also used as an opacifier in porcelain and vitreous enamels. 

Zirconium silicate (zircon). Zircon, ZrSi04, is the main industrial source of zirconium. It is also widely used in production of various types of... 

Zingiberone. See Zingerone Zink Oxide AT, Zinkoxyd Activ . See Zinc oxide Zink Pyrion. See Zinc pyrithione Zipcone CE, Zipcone CG Zipcone UA Zipcone UE. See Silicone elastomer Ziram. See Zinc dimethyidithiocarbamate Zircat. See Zirconium Zircon. See Zirconium silicate Zirconate (2-), bis [carbonate (2-)-0] dihydroxy-diammonium. See Ammonium zirconium carbonate... 

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. 

Zirconium silicate (ZrSiO ) is one form of the mineral whose crystals when polished are known as cubic zircons, which resemble diamond gemstones. 

German chemist Martin Heinrich Klaproth Durable metal highly resistant to heat its mineral zircon, a compound of zirconium silicate, is a semiprecious gem often substituted for diamonds. 

Zirconium silicate occurs in nature as mineral zircon. Ore is mined from natural deposits and concentrated by various techniques (See Zirconium, Recovery). It is separated from sand by electrostatic and electromagnetic methods. 

Zircon, is a zirconium silicate, ZrSi04, with a tetragonal structure IA jamd)... 

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. 

Zircon is native zirconium silicate (ZrSi04) that exhibits beautiful transparent crystals and a Mohs hardness of 7.5. The tetragonal crystals are usually brownish yellow in color. Also known as jargon or jargoon, zircon is a stable and durable silicate crystal. Small crystals of zircon are among the oldest mineral grains ever found on Earth. 

The age of meteorites tells us that the solar system - and therefore the Earth - was born roughly 4.6 billion years ago. The oldest terrestrial rocks are zircone crystals (zirconium silicates) which are 4.2 billion years old, but these stones do not tell us much apart from their age, because they are igneous, or magmatic, rocks whose melting processes have erased any trace of history. Much more interesting are the sedimentary rocks, because these were formed by materials that sank to the bottom of ancient seas, and may still contain remnants of the past. The oldest sediments have been found at Isua, in Greenland, and are 3.8 billion years old, which means that there were immense streches of water on our planet at that time, and that the first oceans had originated many millions of years earlier. 

De Wet A process proposed for extracting zirconium from zircon in the form of zirconium sulfate tetrahydrate. The sodium silicate byproduct should be free from radioactive elements. The key to this process is the formation of an insoluble basic zirconium sulfate as an intermediate. Invented by W. De Wet in South Africa. 

Silicates of zirconium, ZrSi04 (zircon), and hafnium, HfSi04, are the only crystalline phases in the M02-Si02 system. Their fusion with molten Na2Si03 yields double silicates, Na2MSi05 and Na4MSi20g. 

Zirconium is a fairly common element in Earth s crust. Its abundance is estimated to be 150 to 230 parts per million. That places it just below carbon and sulfur among elements occurring in Earth s crust. The two most common ores of zirconium are zircon, or zirconium silicate... 

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). 

Zirconia, see also zirconium dioxide ceramics, 339—340 stabilized, 23, 339—340 Zirconium boride, 345, 346 Zirconium dioxide, 22—23, 374, 387—389 see also zirconia Zirconium silicate, see zircon... 

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