Sample records for chrysoberyl

  1. Diffusion of chromium in chrysoberyl

    NASA Astrophysics Data System (ADS)

    Ahn, Yong-Kil; Seo, Jin-Gyo; Park, Jong-Wan


    Cr 3+ diffusion in chrysoberyl (BeAl 2O 4) irradiated by H + ions and electrons has been studied and compared with diffusion in non-irradiated samples. Chrysoberyl crystals were irradiated with 6 MeV H + ions to fluencies of 1×10 16 cm -2 for 25 min and with 10 MeV electrons to fluencies of 2×10 17 cm -2 for 1 h. Three different types of samples, which were doped with Cr 3+, were annealed in horizontal alumina tube furnaces by 50 K intervals in the temperature range from 1773 to 1923 K for 200 h. Scanning electron microscope-energy dispersive X-ray spectrometer (SEM-EDX) was used to measure the diffusion. Arrhenius equations for the diffusion coefficient for Cr 3+ in the temperature range 1773-1923 K were developed: Electron beam irradiated chrysoberyls, Dcr=2.1×10 -5×exp (-482.3±18.2 kJ mol -1/ RT)m 2 s -1 Proton beam irradiated chrysoberyls, Dcr=2.3×10 -3×exp (-545.4±25.0 kJ mol -1/ RT)m 2 s -1 Natural non-irradiated chrysoberyls Dcr=2.2×10 -3×exp (-547.9±36.8 kJ mol -1/ RT)m 2 s -1 The results indicate that the chromium diffuses deepest into the electron beam irradiated chrysoberyls.

  2. 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.

  3. 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.

  4. 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.

  5. Dielectric constants of chrysoberyl, spinel, phenacite, and forsterite and the oxide additivity rule

    NASA Astrophysics Data System (ADS)

    Shannon, R. D.; Subramanian, M. A.


    The dielectric constants and dielectric loss values of BeAl2O4 (chrysoberyl), MgAl2O4 (spinel), Be2SiO4 (phenacite), and Mg2SiO4 (forsterite) were measured at 1 MHz using a two-terminal method and empirically determined edge corrections. The results are: chrysoberyl, κ' a =9.436, κ' b =9.071, κ' c =8.269; spinel, κ' a =8.18; phenacite, κ' a =6.28, κ' c =6.06; and forsterite, κ' a =6.867, κ' b =7.392, κ' c =6.739. The agreement between measured dielectric polarizabilities as determined from the Clausius-Mosotti equation and those calculated from the sum of oxide polarizabilities according to αD(M2M'X4) = 2αD(MX)+αD(M'X2) is ~ 1.0%.

  6. Explanation of the pressure-induced red shifts of 2E- 4A2 transition line for Cr 3+ ions in the two sites of chrysoberyl

    NASA Astrophysics Data System (ADS)

    Wen-Chen, Zheng


    By using the bond length dependence of covalency reduction factor obtained from the high pressure spectroscopy of ruby (Al 2O 3 : Cr 3+), the pressure-induced shifts of 2E- 4A2 transition line for Cr 3+ ions in both sites (mirror site and inverse site) of chrysoberyl BeAl 2O 4 : Cr 3+ are calculated from the distinctive compressibilities of metal-ligand bond for Cr 3+ ions in the two sites. The results are in reasonable agreement with the observed values. It suggests that the large difference of the pressure-induced shifts of 2E- 4A2 transition line between the Cr 3+ ions at the mirror sites and the inverse sites of chrysoberyl is due mainly to the different average bond compressiblity.

  7. Gahnite, chrysoberyl and beryl co-occurrence as accessory minerals in a highly evolved peraluminous pluton: The Belvís de Monroy leucogranite (Cáceres, Spain)

    NASA Astrophysics Data System (ADS)

    Merino, E.; Villaseca, C.; Orejana, D.; Jeffries, T.


    Gahnite (ZnAl2O4), chrysoberyl (BeAl2O4) and beryl (Be3Al2Si6O18) have been found as accessory minerals in the external, highly fractionated, leucogranitic unit within the Hercynian reversely zoned Belvís de Monroy pluton (westernmost part of the Montes de Toledo batholith, Cáceres, Spain). The highly felsic (SiO2 > 72 wt.%) and peraluminous (ACNK > 1.2) character of this leucogranite, together with the high content of some incompatible elements (F, Li, B, and P), seems to be a primary consequence of fractional crystallization in a magmatic closed-system. The high Be contents and Zn/FeTotal ratio (> 0.01) are relevant factors which have favoured the precipitation of these minerals. Moreover, the Si, Al, P, B, and F activities might be high, favouring the magmatic crystallization of such exotic mineral phases together with Be-rich cordierite, F-rich micas, sillimanite and Al-rich phosphates. In fact, the interplay between the silica and alumina activities likely controls the stabilization and the preferential crystallization of gahnite + chrysoberyl or beryl + chrysoberyl assemblages in mm-sized microdomains. The P-T crystallization conditions are constrained by the muscovite and sillimanite stability fields and the minimum granite Al2O3-saturated solidus, and have been estimated at temperatures between 670 and 700 °C, and pressures between 1 and 2 kbar.

  8. 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.

  9. 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.


    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.

  10. Host Materials for Transition-Metal Ions

    DTIC Science & Technology


    BeA1204 (Chrysoberyl, Cr:BeA204 - Alexandrite ) ..................... 90 15.1 Crystallographic Data on BeA 204 ............................ 9 0 15.2 X...Chrysoberyl, Cr:BeA1 2 04 = Alexandrite ) 15.1 Crystallographic Data on BeA204 Orthorhombic D 16 (Pnma), 62, Z = 4 Orthorhomb__ D2h Ion Site Symmetry x...Stimulated Emission from Alexandrite (BeAl 1204 :Cr 3 +) Sov. J. Quantum Electron. 8 (1978), 671. 2. C. F. Cline, R. C. Morris, M. Dutoit, and P. J

  11. Letters to the Editor: Tunable BeAl2O4:Ti3+ laser

    NASA Astrophysics Data System (ADS)

    Alimpiev, A. I.; Bukin, G. V.; Matrosov, V. N.; Pestryakov, Efim V.; Solntsev, V. P.; Trunov, V. I.; Tsvetkov, E. G.; Chebotaev, V. P.


    A study was made of a tunable laser with a new active medium in the form of a chrysoberyl crystal activated with trivalent titanium ions (BeAl2O4:Ti3+). Lasing due to the 2E-2T2 electronic-vibrational transition in Ti3+ was observed in the wavelength range 0.7-0.9μ when the active medium was pumped by the second harmonic of a YAG:Nd3+ laser (0.5μ).

  12. Physical properties of BeAl6O10 single crystals

    NASA Astrophysics Data System (ADS)

    Pestryakov, E. V.; Petrov, V. V.; Zubrinov, I. I.; Semenov, V. I.; Trunov, V. I.; Kirpichnikov, A. V.; Alimpiev, A. I.


    Single crystals of BeAl6O10, beryllium hexaaluminate, were grown by the Czochralski method. The optical, acousto-optical, elastic, and a number of thermo-mechanical properties of bulk crystals of BeAl6O10 were investigated in comparison with crystal of BeAl2O4, chrysoberyl. It has been demonstrated that this material is the promising host for active media of tunable solid state lasers.

  13. Czochralski growth of tunable laser crystal BeAl(sub)2O(sub)4:Cr(sup)3+

    NASA Astrophysics Data System (ADS)

    Ma, X.; Hou, Y.; Wang, S.; Shen, Y.; Jin, Z.


    Optically homogeneous alexandrite blanks, 100 mm in length and 20 mm in diameter, were grown by Czochralski technique using RF heating. These blanks were fabricated into 90 mm long 5 mm diameter c-axis laser rods. Tunable laser output was obtained experimentally. Spectroscopic characteristics of the crystal were presented. Problems such as prevention of BeO contamination, chrysoberyl formation kinetics and melt aging are also discussed.

  14. 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.

  15. SOLID-STATE AND LIQUID LASERS: Generation of tunable radiation in a BeAl2O4:Ti3+ laser subjected to pulsed coherent pumping at a high repetition frequency

    NASA Astrophysics Data System (ADS)

    Pestryakov, Efim V.; Trunov, V. I.; Alimpiev, A. I.


    Coherent pumping of a titanium-activated chrysoberyl laser, by the second harmonic of a continuously pumped YAG:Nd laser operating in the Q-switched regime at a pulse repetition frequency 3-15 kHz, made it possible to achieve a conversion efficiency of ~5% and tuning of the emission wavelength in the range 0.73-0.95 µ. It was found experimentally that the lifetime of an excited state of the Ti3+ ions decreased on increase in temperature from 4.9 µsec at 300 K to 0.2 µsec at 500 K.

  16. Discrimination of zeolites and beryllium containing silicates using portable Raman spectroscometric equipment with near-infrared excitation.


    Jehlička, J; Vandenabeele, P; Edwards, H G M


    In this paper Raman spectra were obtained for a series of zeolites (thomsonite, stilbite, natrolite) and beryllium containing silicates (beryl, chrysoberyl, euclase, phenacite, bavenite, milarite) using a portable Raman specrometer with a 785 nm laser excitation to show the possibility to apply this setting for unambiguous detection and discrimination of these silicate minerals. Obtained spectra contain the most intense Raman bands at the same positions ±2-4 cm(-1) as reported in the literature. The use of these bands permits the unambiguous identification of these phases. Data show the possibility to discriminate individual species of similar whitish color and aspect. Measurements showed an excellent correspondence of Raman bands obtained using the portable system and a laboratory Raman microspectrometer (with the same excitation laser wavelenght). However, for several minerals of these groups (chrysoberyl, bertrandite, chiavennite) Raman spectra were not of sufficient quality to permit unambiguous identification. The reasons are discussed. Raman spectrum of chiavennite CaMnBe(2)Si(5)O(13)(OH)(2)·2(H(2)O) - a transformation product occurring together with bavenite on the surface of beryl crystals was obtained for the first time using the laboratory Raman spectrometer.

  17. 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.

  18. 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.

  19. Electron magnetic resonance investigation of chromium diffusion in yttria powders

    NASA Astrophysics Data System (ADS)

    de Biasi, R. S.; Grillo, M. L. N.


    The electron magnetic resonance (EMR) technique was used to investigate the diffusion of chromium in yttria (Y 2O 3) powders. The EMR absorption intensity was measured for several annealing times and three different temperatures of isothermal annealing: 1273, 1323 and 1373 K. The activation temperature for diffusion, calculated from the experimental data using a theoretical model based on the Fick equation, was found to be E A=342±5 kJ mol -1. This value is larger than the activation energy for the diffusion of chromium in rutile (TiO 2), periclase (MgO) and cobalt monoxide (CoO) and smaller than the activation energy for the diffusion of chromium in chrysoberyl (BeAl 2O 4).

  20. 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.

  1. Investigation of synthesized Be-bearing silicate glass as laboratory reference sample at X-ray electron probe microanalysis of silicates

    NASA Astrophysics Data System (ADS)

    Belozerova, Olga Yu.; Mikhailov, Mikhail A.; Demina, Tamara V.


    The article discusses estimates of the stability and homogeneity in Be-Mg-Al-silicate glass produced by the authors and its applicability as a laboratory reference sample for X-ray electron probe microanalysis (EPMA) of Be-bearing silicate matters: crystals and quenching melt (glasses), silicates and oxides. The results were obtained using Superprobe-733 and Superprobe JXA-8200 (JEOL Ltd, Japan) devices. The sample homogeneity was studied on macro (10-100 μm) and micro (1-10 μm) levels and was evaluated by the scheme of dispersion analysis. The applicability of Be-bearing silicate glass as a reference sample for Mg, Al, Si determinations was tested on the international certified reference glasses and laboratory reference samples of minerals with a known composition. The obtained experimental metrological characteristics correspond to the "applied geochemistry" type of analysis (second category) and suggest that Be-bearing silicate glass is appropriate as a laboratory reference sample for EPMA of Be-bearing silicate matters, silicates and oxides. Using Be-Mg-Al-silicate glass as a reference sample we obtained satisfactory data on the composition of both some minerals including cordierite and beryllium cordierite, beryllium indialite, beryl and metastable phases (chrysoberyl, compounds with structure of β-quartz and petalite).

  2. 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