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Davisite, CaScAlSiO_6, a new pyroxene from the Allende meteorite

Ma, Chi and Rossman, George R. (2009) Davisite, CaScAlSiO_6, a new pyroxene from the Allende meteorite. American Mineralogist, 94 (5-6). pp. 845-848. ISSN 0003-004X.

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Davisite, ideally CaScAlSiO_6, is a new member of the Ca clinopyroxene group, where Sc^(3+) is dominant in the M1 site. It occurs as micro-sized crystals along with perovskite and spinel in an ultra-refractory inclusion from the Allende meteorite. The mean chemical composition determined by electron microprobe analysis is (wt%) SiO_2 26.24, CaO 23.55, Al_2O_3 21.05, Sc_2O_3 14.70, TiO_2 (total) 8.66, MgO 2.82, ZrO_2 2.00, Y_2O_3 0.56, V_2O_3 0.55, FeO 0.30, Dy_2O_3 0.27, Gd_2O_3 0.13, Er_2O_3 0.08, sum 100.91. Its empirical formula calculated on the basis of 6 O atoms is Ca_(0.99)(Sc_(0.50)Ti^(3+)0.16^(Mg)0.16Ti^(4+)0.10 Zr_(0.04)V^(3+)_(0.02)Fe^(2+)_(0.01)Y_(0.01))_(∑1.00)(Si_(1.03)Al_(0.97))_(∑2).00O_6. Davisite is monoclinic, C2/c; a = 9.884 Å, b = 8.988 Å, c = 5.446 Å, β =105.86°, V = 465.39 Å^3, and Z = 4. Its electron back-scattered diffraction pattern is an excellent match to that of synthetic CaScAlSiO6 with the C2/c structure. The strongest calculated X-ray powder diffraction lines are [d spacing in Å (I) (hkl)]: 3.039 (100) (221), 2.989 (31) (310), 2.943 (18) (311), 2.619 (40) (002), 2.600 (26) (131), 2.564 (47) (221), 2.159 (18) (331), 2.137 (15) (421), 1.676 (20) (223), and 1.444 (18) (531). The name is for Andrew M. Davis, a cosmochemist at the University of Chicago, Illinois.

Item Type:Article
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Ma, Chi0000-0002-1828-7033
Rossman, George R.0000-0002-4571-6884
Additional Information:© 2009 Mineralogical Society of America. Manuscript received February 4, 2009. Manuscript accepted February 18, 2009. Manuscript handled by bryan chakouMakos. The Caltech Analytical Facility at the Division of Geological and Planetary Sciences is supported, in part, by grant NSF EAR-0318518 and the MRSEC Program of the NSF under DMR-0080065. Funding from NSF grant EAR-0337816 is also acknowledged. We thank Alan Rubin and Kimberly Tait for reviewing this manuscript.
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Subject Keywords:Davisite; CaScAlSiO6; new mineral; Sc-rich pyroxene; refractory phase; ultra-refractory inclusion; Allende meteorite
Issue or Number:5-6
Record Number:CaltechAUTHORS:20090915-112159755
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Official Citation:Ma, Chi, Rossman, George R. Davisite, CaScAlSiO6, a new pyroxene from the Allende meteorite American Mineralogist 2009 94: 845-848
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:15855
Deposited By: Ruth Sustaita
Deposited On:02 Oct 2009 21:27
Last Modified:09 Mar 2020 13:19

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