Welcome to the new version of CaltechAUTHORS. Login is currently restricted to library staff. If you notice any issues, please email coda@library.caltech.edu
Published 2009 | Published
Journal Article Open

Davisite, CaScAlSiO_6, a new pyroxene from the Allende meteorite

Abstract

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.

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.

Attached Files

Published - Ma2009p4299Am_Mineral.pdf

Files

Ma2009p4299Am_Mineral.pdf
Files (1.1 MB)
Name Size Download all
md5:45d95821ddfe84a32fa99fb715ca5193
1.1 MB Preview Download

Additional details

Created:
August 22, 2023
Modified:
October 19, 2023