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    Chrysoberyl Beal O: Crystal Data

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    p6a4ndu
    Chrysoberyl is an orthorhombic mineral with the chemical formula BeAl2O4 that commonly forms tabular crystals on {001} faces or short prismatic crystals along [100] up to 22 cm in size. It has a distinct cleavage on {110}, imperfect cleavage on {010}, and poor cleavage on {001}. Chrysoberyl is transparent to translucent, and can exhibit various shades of green, yellow, brownish to greenish black, or raspberry-red colors. It occurs in granite pegmatites associated with high-grade mica schists or reaction zones in ultramafic rocks, and is also found detritally in placers.

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    Chrysoberyl Beal O: Crystal Data

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    p6a4ndu
    44 views1 page
    Chrysoberyl is an orthorhombic mineral with the chemical formula BeAl2O4 that commonly forms tabular crystals on {001} faces or short prismatic crystals along [100] up to 22 cm in size. It has a distinct cleavage on {110}, imperfect cleavage on {010}, and poor cleavage on {001}. Chrysoberyl is transparent to translucent, and can exhibit various shades of green, yellow, brownish to greenish black, or raspberry-red colors. It occurs in granite pegmatites associated with high-grade mica schists or reaction zones in ultramafic rocks, and is also found detritally in placers.

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    chrysoberyl

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    chrysoberyl

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    Chrysoberyl is an orthorhombic mineral with the chemical formula BeAl2O4 that commonly forms tabular crystals on {001} faces or short prismatic crystals along [100] up to 22 cm in size. It has a distinct cleavage on {110}, imperfect cleavage on {010}, and poor cleavage on {001}. Chrysoberyl is transparent to translucent, and can exhibit various shades of green, yellow, brownish to greenish black, or raspberry-red colors. It occurs in granite pegmatites associated with high-grade mica schists or reaction zones in ultramafic rocks, and is also found detritally in placers.

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    44 views1 page

    Chrysoberyl Beal O: Crystal Data

    Uploaded by

    p6a4ndu
    Chrysoberyl is an orthorhombic mineral with the chemical formula BeAl2O4 that commonly forms tabular crystals on {001} faces or short prismatic crystals along [100] up to 22 cm in size. It has a distinct cleavage on {110}, imperfect cleavage on {010}, and poor cleavage on {001}. Chrysoberyl is transparent to translucent, and can exhibit various shades of green, yellow, brownish to greenish black, or raspberry-red colors. It occurs in granite pegmatites associated with high-grade mica schists or reaction zones in ultramafic rocks, and is also found detritally in placers.

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    Chrysoberyl BeAl2 O4

    c 2001-2005 Mineral Data Publishing, version 1

    Crystal Data: Orthorhombic. Point Group: 2/m 2/m 2/m. Crystals are tabular
    on {001} or short prismatic along [100], to 22 cm; prominently striated on {001} k [100].
    Twinning: Common on {130}, producing either flattened heart-shaped or pseudohexagonal
    multiple contact and penetration twins.
    Physical Properties: Cleavage: Distinct on {110}, imperfect on {010}, poor on {001}.
    Fracture: Uneven to conchoidal. Tenacity: Brittle. Hardness = 8.5 D(meas.) = 3.75(1)
    D(calc.) = 3.69
    Optical Properties: Transparent to translucent, may be opaque and chatoyant with
    oriented inclusions. Color: Various shades of green, yellow, brownish to greenish black, may be
    raspberry-red under incandescent light when chromian; colorless, pale shades of yellow, green, or
    red in transmitted light. Streak: White. Luster: Vitreous.
    Optical Class: Biaxial (+). Pleochroism: X = red; Y = yellow-orange; Z = emerald-green.
    Orientation: X = c; Y = b; Z = a. Dispersion: r > v. α = 1.746 β = 1.748 γ = 1.756
    2V(meas.) = 70◦
    Cell Data: Space Group: P bnm. a = 4.428(1) b = 9.415(3) c = 5.481(2) Z=4
    X-ray Powder Pattern: Near Golden, Colorado, USA. (ICDD 11-448).
    3.24 (100), 2.091 (90), 1.619 (80), 4.01 (50), 2.563 (50), 2.265 (45), 2.081 (45)
    Chemistry: (1) (2)
    TiO2 0.55
    Al2 O3 76.34 80.30
    FeO 3.60
    BeO 19.15 19.70
    LOI 0.30
    Total 99.94 100.00
    (1) Near Golden, Colorado, USA. (2) BeAl2 O4 .
    Occurrence: Characteristic of some granite pegmatites associated with high-grade mica schists
    or reaction zones in ultramafic rocks; also detrital in placers.
    Association: Quartz, muscovite, albite, beryl, columbite, tourmaline, topaz, kyanite, staurolite
    (granite pegmatites); phenakite, apatite, tourmaline, fluorite (reaction zone pegmatites).
    Distribution: Widespread, however fine crystals are uncommon. Notable localities include:
    from many places in Brazil, with exceptional crystals from Tancredo, Itaguaçu, and Colatina,
    Espirito Santo; from Faria Lemos, Santa Luzia de Carangola, and Americana, Teófilo Otoni,
    Minas Gerais; at Campo Formoso, Teixeira de Freitas, and Cachoeira, Bahia. From Maršı́kov,
    Czech Republic. At the Izumrudnye mines, Tokovaya River, near Yekaterinburg (Sverdlovsk),
    and Mursinka, Ural Mountains, Russia. From Miakanjovato, near Lake Alaotra, northeast of
    Ambatosoratra, Madagascar. Near Masvingo (Ft. Victoria), Zimbabwe. Abundant in gem gravel
    placers in the Ratnapura district, Sri Lanka. In the USA, from near Golden, Jefferson Co.,
    Colorado; in Maine, at Topsham, Sagadahoc Co., from Paris, Norway, and Hartford, Oxford Co.,
    and elsewhere.
    Name: From the Greek for golden, in allusion to the mineral’s color, and beryl.
    References: (1) Palache, C., H. Berman, and C. Frondel (1944) Dana’s system of mineralogy,
    (7th edition), v. I, 718–722. (2) Vlasov, K.A., Ed. (1966) Mineralogy of rare elements, v. II,
    73–77. (3) Farrell, E.F., J.H. Fang, and R.E. Newnham (1963) Refinement of the chrysoberyl
    structure. Amer. Mineral., 48, 804–810. (4) Hazen, R.M. (1987) High-pressure crystal chemistry of
    chrysoberyl, Al2 BeO4 : insights on the origin of olivine elastic anisotropy. Phys. Chem. Minerals,
    14, 13–20. (5) Pilati, T., F. Demartin, F. Cariati, S. Bruni, and C.M. Gramaccioli (1993) Atomic
    thermal parameters and thermodynamic functions for chrysoberyl (BeAl2 O4 ) from vibrational
    spectra and transfer of empirical force fields. Acta Cryst., 49, 216–222.
    All rights reserved. No part of this publication may be reproduced, stored in a retrieval system or transmitted in
    any form or by any means, electronic, mechanical, photocopying, recording, or otherwise without the prior written
    permission of Mineral Data Publishing.

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