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Sample records for chrysoberyl

  1. Radioactivity of neutron-irradiated cat's-eye chrysoberyls

    Science.gov (United States)

    Tang, S. M.; Tay, T. S.

    1999-04-01

    The recent report of marketing of radioactive chrysoberyl cat's-eyes in South-East Asian markets has led us to use an indirect method to estimate the threat to health these color-enhanced gemstones may pose if worn close to skin. We determined the impurity content of several cat's-eye chrysoberyls from Indian States of Orissa and Kerala using PIXE, and calculated the radioactivity that would be generated from these impurities and the constitutional elements if a chrysoberyl was irradiated by neutrons in a nuclear reactor for color enhancement. Of all the radioactive nuclides that could be created by neutron irradiation, only four ( 46Sc, 51Cr, 54Mn and 59Fe) would not have cooled down within a month after irradiation to the internationally accepted level of specific residual radioactivity of 2 nCi/g. The radioactivity of 46Sc, 51Cr and 59Fe would only fall to this safe limit after 15 months and that of 54Mn could remain above this limit for several years.

  2. Radioactivity of neutron-irradiated cat's-eye chrysoberyls

    Energy Technology Data Exchange (ETDEWEB)

    Tang, S.M. E-mail: phytsm@leonis.nus.edu.sg; Tay, T.S

    1999-04-02

    The recent report of marketing of radioactive chrysoberyl cat's-eyes in South-East Asian markets has led us to use an indirect method to estimate the threat to health these color-enhanced gemstones may pose if worn close to skin. We determined the impurity content of several cat's-eye chrysoberyls from Indian States of Orissa and Kerala using PIXE, and calculated the radioactivity that would be generated from these impurities and the constitutional elements if a chrysoberyl was irradiated by neutrons in a nuclear reactor for color enhancement. Of all the radioactive nuclides that could be created by neutron irradiation, only four ({sup 46}Sc, {sup 51}Cr, {sup 54}Mn and {sup 59}Fe) would not have cooled down within a month after irradiation to the internationally accepted level of specific residual radioactivity of 2 nCi/g. The radioactivity of {sup 46}Sc, {sup 51}Cr and {sup 59}Fe would only fall to this safe limit after 15 months and that of {sup 54}Mn could remain above this limit for several years.

  3. Mariinskite, BeCr2O4, a new mineral, chromium analog of chrysoberyl

    Science.gov (United States)

    Pautov, L. A.; Popov, M. P.; Erokhin, Yu. V.; Khiller, V. V.; Karpenko, V. Yu.

    2013-12-01

    A new mineral, mariinskite, BeCr2O4, the chromium analog of chrysoberyl, has been found at the Mariinsky (Malyshevo) deposit, the Ural Emerald Mines, the Central Urals, Russia. The mineral is named after its type locality. It was discovered in chromitite in association with fluorphlogopite, Cr-bearing muscovite, eskolaite, and tourmaline. Mariinskite occurs as anhedral grains ranging from 0.01 to 0.3 mm in size; in some cases it forms pseudohexagonal chrysoberyl-type twins. The mineral is dark-green, with a pale green streak; the Mohs' hardness is 8.5, microhardness VHN = 1725 kg/mm2. D meas = 4.25(2) g/cm3, D calc = 4.25 g/cm3. Microscopically, it is emerald-green, pleochroic from emerald-green (γ) to yellow-green (β) and greenish yellow (α). The new mineral is biaxial (+), γ = 2.15(1), β = 2.09(3), and α = 2.05(1), 2 V meas = 80 ± (10)°, 2 V calc = 80.5°. In reflected light, it is gray with green reflections; R max (589) = 12.9%; R min (589) = 12.3%, and there are strong, internal green reflections. The strongest absorption bands in the IR spectrum are as follows (cm-1): 935, 700, 614, 534. Space group Pnma, a = 9.727(3), b = 5.619(1), c = 4.499(1) Å, V = 245.9(3) Å3, Z = 4. The strongest reflections in the X-ray powder diffraction pattern are as follows ( d Å, I, hkl): 4.08(40)(101), 3.31(90)(111), 2.629(50)(301), 2.434(50)(220), 2.381(40)(311), 2.139(60)(221), 1.651(100)(222). The average chemical composition of mariinskite (electron microprobe, wt %) is as follows: BeO 16.3, Al2O3 23.89, Cr2O3 58.67, Fe2O3 0.26, V2O3 0.26, TiO2 0.61, total is 99.98. The empirical formula, calculated on the basis of four O atoms is Be1.03(Cr1.22Al0.74Ti0.01Fe0.01V0.01)1.99O4. The compatibility index 1 - (Kp/Kc), 0.019, is excellent. The type specimens are deposited in the Fersman Mineralogical Museum, Russian Academy of Sciences, Moscow, and the Ural Geological Museum, Yekaterinburg, Russia.

  4. Trace elements in corundum, chrysoberyl, and zircon: Application to mineral exploration and provenance study of the western Mamfe gem clastic deposits (SW Cameroon, Central Africa)

    Science.gov (United States)

    Kanouo, Nguo Sylvestre; Ekomane, Emile; Yongue, Rose Fouateu; Njonfang, Emmanuel; Zaw, Khin; Changqian, Ma; Ghogomu, Tanwi Richard; Lentz, David R.; Venkatesh, Akella Satya

    2016-01-01

    Trace element abundances in three indicator minerals (corundum, chrysoberyl, and zircon grains) from the western Mamfe gem placers, as determined by LA-ICP-MS analytical techniques, are shown to be sensitive to their crystallization conditions and source rock types. Corundum is dominantly composed of Al (standardized at 529,300 ppm), Fe (2496-12,899 ppm), and Ti (46-7070 ppm). Among element ratios, Fe/Mg (73-1107), Fe/Ti (0.5-245.0), Ti/Mg (1-175), and Ga/Mg (4-90) are generally higher whereas, Cr/Ga ( Nb in the western Mamfe chrysoberyls show that they were crystallized in granitic pegmatites, with some of those source rocks being enriched in Ta and Sn. Zirconium oxide (ZrO2: standardized at 66.1 wt.%)) is the only major oxide in analysed coarse-grained zircons. Within the minor elementary suites: Hf (4576-12,565 ppm) and Y (48-2805 ppm) contents are significantly high. The trace element suites include: Th (7-1565 ppm), U (13-687 ppm), and ∑REE (50-2161 ppm), whose values are significantly low. The (Yb/Sm)N, Ce/Ce*, and Eu/Eu* anomalies range from 1.0 to 227.0, 0 to 308, and 0.08 to 1.7 respectively. They are Hf-Y-HREE enriched and depleted zircons mainly crystallized in magmatic oxidized environments. They were mainly sorted from granitoids, syenites and kimberlites.

  5. Heat capacities and thermodynamic functions for beryl, Be3Al2Si6O18, phenakite, Be2SiO4, euclase, BeAlSiO4(OH), bertrandite, Be4Si2O7(OH)2, and chrysoberyl, BeAl2O4.

    Science.gov (United States)

    Hemingway, B.S.; Barton, M.D.; Robie, R.A.; Haselton, H.T., Jr.

    1986-01-01

    The heat capacities of beryl, phenakite, euclase and bertrandite have been measured between approx 5 and 800 K by combined quasi-adiabatic cryogenic calorimetry and differential scanning calorimetry. The heat capacities of chrysoberyl have been measured from 340 to 800 K. The resulting data have been combined with solution and phase-equilibrium experimental data and simultaneously adjusted using the programme PHAS20 to provide an internally consistent set of thermodynamic properties for several important beryllium phases. The experimental heat capacities and tables of derived thermodynamic properties are presented.-J.A.Z.

  6. The Taser Induced Fluorescence Spectra And Decay Lifetime Of NI2+ Doped Chrysoberyl

    Science.gov (United States)

    Hanting, Ji; Genwang, Wen; Jun, Oian; Zhende, Chen; Wenbin, Gao; Songhao, Lui

    1985-12-01

    This paper reports the experimental results on the fluorescence spectra and decay lifetime of 3T2---3A2 vibronic transition of NI2+ : BeAl204 with LIFM. The center wavelength of fluorescence spectra is 1.33u , the bandwidth (FWHM) is 0.14u (1.26 - 1.40u), and the center red-shift of fluorescence spectra in relative to absorption spectra is 0.225u at room temperature (300k). The radiation lifetime is 3T2 band is 198 us.

  7. Multi-element analysis of sediments, coal samples and gemstones by INAA

    International Nuclear Information System (INIS)

    Instrumental Neutron Activation Analysis (INAA) is one of the best analytical methods for the determination of most of the Rare Earth Elements (REEs) and other trace elements. INAA is more effective for trace elemental analysis in the presence of other elements in varying matrices. Multi elemental analysis of the sediments of Gosthani River Estuary, Balacheruvu Backwaters, Kothagudem coal deposits and Chrysoberyl, chrysoberyl cat's eye and Alexandrite gemstones were carries out by INAA. (author)

  8. On solid-phase interaction of beryllium oxide with mullite

    International Nuclear Information System (INIS)

    The interaction of beryllium oxide with mullite has been analyzed thermodynamically. It is shown that the reaction between the above substances must proceed with separation of chrysoberyl but without yielding phenacite, which is inconsistent with some data published. It has been found experimentally that the interaction of pure BeO and mullite is described by equation 3Al2Ox2SiO2+3BeO→3BeAl2O4+2SiO2

  9. Brazilian gemstones

    Science.gov (United States)

    Franco, Rui Ribeiro

    1981-04-01

    Brazil counts as a gemmological province because of the variety of gem minerals present in the country. Most Brazilian states and territories produce gemstones, the State of Minas Gerais being the most important producer both in volume and in number of species. Diamonds are chiefly derived by panning from alluvial deposits in Minas Gerais, Mato Grosso and Goiás. Among other gemstones, the most important are aquamarines, beryls, chrysoberyls, topazes, amethysts, tourmalines, emeralds and agates, and their respective varieties. The occurrences of these gemstones, as well as of a great number of others, are described for each state in which they are found.