Sample records for chrysoberyl

  1. Recrystallization of natural chrysoberyl in multicomponent melts

    NASA Astrophysics Data System (ADS)

    Gromalova, N. A.; Mal'tsev, V. V.; Dorokhova, G. I.; Leonyuk, N. I.; Urusov, V. S.


    Chrysoberyl and alexandrite crystals have been grown from solutions in melts based on the Li2CO3-MoO3, Bi2O3-MoO3, PbO-V2O5, Na2B4O7, and K2MoO4-MoO3 systems using natural alexandrite and chrysoberyl debris as the initial BeAl2O4 compound. An analysis of the morphology and homogeneity of the crystals grown has revealed the Bi2O3-MoO3 solvent to be the most appropriate. The optimal color characteristics ("quality" of alexandrite effect) manifest themselves when adding about 5 mol % Cr2O3. The largest crystals (up to 10 mm in size) were obtained from a solution in melt based on PbO-V2O5 at a ratio of the crystal-forming component to the solvent of 9: 91 wt %; These characteristics, along with a relatively low operating temperature (970°C), give grounds to consider this type of solvent promising.

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

    NASA Astrophysics Data System (ADS)

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


    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.

  3. Morphology of synthetic chrysoberyl and alexandrite crystals: Analysis of experimental data and theoretical modeling

    NASA Astrophysics Data System (ADS)

    Gromalova, N. A.; Eremin, N. N.; Dorokhova, G. I.; Urusov, V. S.


    A morphological analysis of chrysoberyl and alexandrite crystals obtained by flux crystallization has been performed. Seven morphological types of crystals are selected. The surface energies of the faces of chrysoberyl and alexandrite crystals and their isostructural analogs, BeCr2O4 and BeFe2O4, have been calculated by atomistic computer modeling using the Metadise program. A "combined" approach is proposed which takes into account both the structural geometry and the surface energy of the faces and thus provides better agreement between the theoretical and experimentally observed faceting of chrysoberyl and alexandrite crystals.

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

    NASA Astrophysics Data System (ADS)

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


    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.

  5. 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)

    NASA Astrophysics Data System (ADS)

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


    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 (<0.072) is low. The Fe (≤12,899), Ga (≤398), Mg (2-62), Cr (1.1-33.0), and V (3.0-93.0) contents (in ppm) mostly typify corundum grains formed in magmatic rocks, although some are metamorphic affiliated. A very higher Ti and significantly low Ga, Ta and Nb contents in some blue grains, suggest interesting concentrations of those high-tech metals in their source rocks. Chrysoberyl is dominantly composed of Al (standardized at 425,000 ppm) and Be (62701-64371 ppm). Iron (7605-9225 ppm), Sn (502-3394 ppm), and Ti (33-2251 ppm) contents are high, whereas Ga (333-608 ppm), Ta (<456.0 ppm), and Nb (<3.0 ppm) are significantly low. The high (Be and Sn) and significantly low Ga-Rb abundances, and Ta > 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.

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

    USGS Publications Warehouse

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


    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.

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

    NASA Astrophysics Data System (ADS)

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


    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.

  8. Katzenaugen und Sternsteine: Spielwiese

    NASA Astrophysics Data System (ADS)

    Ucke, Christian; Schlichting, Hans-Joachim


    Edelsteine vom Typ Chrysoberyll sind auch unter der Kurzbezeichnung Katzenauge bekannt. Im Chrysoberyll eingelagert sind feine, parallel angeordnete, metallisch glänzende Nadeln aus Rutil (Titandioxid). Auch Hohlkanäle und Risse durchziehen das Material. Lichtreflexion an diesen Einlagerungen und Kanälen erklärt das Lichtband, das dem Stein zu seinem Namen verhalf.

  9. Brazilian gemstones

    NASA Astrophysics Data System (ADS)

    Franco, Rui Ribeiro


    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.

  10. Beryllium deposits of the western Seward Peninsula, Alaska

    USGS Publications Warehouse

    Sainsbury, C.L.


    Deposits of beryllium ore in the Lost River area of the western Seward Peninsula, Alaska, consist of replacement veins, pipes, and stringer lodes is limestone in a zone about 7 miles long and 2 to 3 miles wide which is faulted and intruded by dikes and stocks. The ores are remarkably alike and typically consist of the following minerals, in percent: fluorite, 45-65; diaspore, 5-10; tourmaline, 0-10; chrysoberyl, 3-10; white mica, 0-5; small amounts of hematite, sulfide minerals, manganese oxide, other beryllium minerals; and traces of minerals not yet identified. The ores generally are cut by late veinlets which are of the same mineralogy as the groundmass ore, or which consist of fluorite, white mica, and euclase. The ores are fine grained, and many of the individual mineral grains, except fluorite, are less than 1 mm in size. The beryllium content of bulk samples of ore ranges from 0.11 to 0.54 percent (0.31 to 1.50 percent BeO). High-grade nodules, composed principally of chrysoberyl, diaspore, fluorite, and mica, contain as much as 6 percent BeO. Geochemical reconnaissance has disclosed other areas of anomalous beryllium in stream sediments elsewhere on the Seward Peninsula, generally around biotite granites that have them associated with tin deposits; additional exploration probably will disclose other deposits.

  11. Solution of rocks and refractory minerals by acids at high temperatures and pressures. Determination of silica after decomposition with hydrofluoric acid

    USGS Publications Warehouse

    May, I.; Rowe, J.J.


    A modified Morey bomb was designed which contains a removable nichromecased 3.5-ml platinium crucible. This bomb is particularly useful for decompositions of refractory samples for micro- and semimicro-analysis. Temperatures of 400-450?? and pressures estimated as great as 6000 p.s.i. were maintained in the bomb for periods as long as 24 h. Complete decompositions of rocks, garnet, beryl, chrysoberyl, phenacite, sapphirine, and kyanite were obtained with hydrofluoric acid or a mixture of hydrofluoric and sulfuric acids; the decomposition of chrome refractory was made with hydrochloric acid. Aluminum-rich samples formed difficultly soluble aluminum fluoride precipitates. Because no volatilization losses occur, silica can be determined on sample solutions by a molybdenum-blue procedure using aluminum(III) to complex interfering fluoride. ?? 1965.

  12. The cosmochemical behavior of beryllium and boron

    NASA Astrophysics Data System (ADS)

    Lauretta, Dante S.; Lodders, Katharina


    The chemistry of Be and B in the solar nebula is reinvestigated using thermodynamic equilibrium calculations. The dominant Be gases are monatomic Be at high temperatures and the hydroxides BeOH and Be(OH)2 at lower temperatures. Beryllium condenses as gugiaite (Ca2BeSi2O7) in solid solution with melilite with a 50% condensation temperature of 1490 K. If an ideal solid solution of chrysoberyl (BeAl2O4) into spinel is assumed, most of the Be condenses into spinel, yielding a 50% condensation temperature of 1501 K. However, the difference in the crystal structures of spinel and chrysoberyl indicates that their solid solution may be non-ideal. At high temperatures the dominant B gases are BO, HBO, and HBO2, while NaBO2, KBO2, and LiBO2 are dominant at lower temperatures. Boron is less refractory than Be and is calculated to condense into solid solution with feldspar. The majority of B condenses as danburite (CaB2Si2O8) in solid solution with anorthite. At lower temperatures, when the feldspar composition is more albitic, the remaining B condenses as reedmergnerite (NaBSi3O8). The 50% condensation temperature of B is 964 K. The 50% condensation temperature of B is similar to that of Na and much higher than that of S. Therefore, normalized B abundances in chondrites are expected to correlate with Na abundances. Be is predicted to be concentrated in melilite, a conclusion which is consistent with the few measurements of Be concentrations in calcium aluminum-rich inclusions (CAIs). Boron is predicted to be concentrated in feldspar, but no analytical data are available to test this prediction.

  13. Magnetoferroelectrics, divertable ferroelectrics and pyroelectric glass-ceramics

    NASA Astrophysics Data System (ADS)

    Halliyal, A. G.; Newnham, R. E.; Cross, L. E.; Bhalla, A. S.


    During the past three years the major topics on which work was carried out under the above contract are (1) grain oriented glass-ceramics for piezoelectric and pyroelectric devices, (2) shape memory in PLZT ceramics, and (3) magnetoferroelectric effect. Several glass-ceramic compositions were developed which showed a high figure of merit for application in pyroelectric devices. They are also good candidate materials for piezoelectric resonators, and surface acoustic wave devices. In the report, the compositions, processing methods and advantages of glass-ceramics over single crystals for use in devices are classified at length. A connectivity model was developed for the prediction of piezoelectric and pyroelectric properties of multicomponent glass-ceramics. Shape-memory effect in metals and alloys is a well known phenomenon. It is the recovery of a plastically deformed material to its original shape by heating. Under the above program, shape-memory effect in PLZT ceramics was investigated. Another highlight of the past three years was the discovery of a new class of ferroelectric materials possessing a magnetically induced ferroelectricity called 'magnetoferroelectricity'. A magnetoferroelectric develops a reversible spontaneous electric polarization on passing through a magnetic phase transition. The effect was demonstrated in chromium chrysoberyl Cr2BeO4.

  14. Mineral and fluid inclusion study of emeralds from the Lake Manyara and Sumbawanga deposits, Tanzania

    NASA Astrophysics Data System (ADS)

    Moroz, I.; Vapnik, Y.; Eliezri, I.; Roth, M.


    Mineral and fluid inclusions were investigated in Tanzanian emeralds sampled in the Lake Manyara and Sumbawanga deposits. Microthermometry and Raman microprobe analyses were applied for this study. Primary and pseudosecondary H 2O-CO 2 inclusions, with numerous daughter solid phases, are common in the emeralds from the Lake Manyara deposit. Magnesite, Mg-calcite, aragonite, dolomite, calcite, nahcolite, quartz and chrysoberyl were identified as trapped solids in fluid inclusions. Similar mineral inclusions were also found in the emeralds themselves. The composition of the trapped fluid present at emerald growth is estimated to be a carbonic-rich solution with chloride content of about 6 wt% NaCl equiv. The P-T conditions of emerald growth are as follows: T = 370-470°C and P=3.0-7.0 kbar. Mineral inclusions of phenakite, euclase, bertrandite and helvite are common in the emeralds of the Sumbawanga deposit. CO 2-rich inclusions with an aqueous phase (usually below the detection limit), and CaCl 2-rich inclusions with salinity of up to 17 wt% NaCl equiv. are related to emerald growth. The trapping of fluid inclusions postdates the growth of mineral inclusions. The P-T conditions of emerald growth are as follows: T = 220-300°C and P = 0.7-3.0 kbar.

  15. Pegmatites of the Crystal Mountain district, Larimer County, Colorado

    USGS Publications Warehouse

    Thurston, William R.


    The Front Range of Colorado is composed chiefly of schists of the pre-Cambrian Idaho Springs formation which have been intruded by a variety of granitic batholiths. In the Crystal Mountain district the Mount Olympus granite, a satellite of the Longs Peak batholith, forms sills and essentially concordant multiple intrusions in quartz-mica schist that dips southward at moderate to steep angles. A great number of pegmatites accompanied and followed the intrusion of the sills, and formed concordant and discordant bodies in schist and granite. Over 1,300 pegmatites in the Hyatt area north of the Big Thompson River are mapped and individually described. There are 27 pegmatites in the area that are made up of a wall zone and a core, and one, the pegmatite at the Hyatt mine, is composed of five zones. The largest pegmatites in the area are discordant in schist and occupy zones that are interpreted to be tear faults and tension fractures produced by the successive intrusions of granite that formed multiple sills. The majority of pegmatites in the large multiple sills were emplaced along the foliation and fractures. The composition of 96 percent of the pegmatites is granitic, 3.5 percent are quartz-rich pegmatites, and a few are tourmaline-rich. The pegmatites were intruded over a period of time and probably were derived from a granitic magma at different stages during differentiation. Solutions escaping from many of the pegmatites tournalinized and silicified the wall rocks for a few inches to two feet, but chemical and spectrographic analyses fail to show the transport of any other constituents. Perthite, plagioclase, and quartz are the essential minerals of the pegmatites, and muscovite is a minor but widespread constituent. Tourmaline, garnet, beryl, and apatite are common accessory minerals, and lithiophillitite-triphylite, bismuthinite, uraninite, columbite-tantalite, and chrysoberyl are rare constituents. Beryl is found in 250 or 27 percent of the pegmatites and makes