Abstract
Grossmanite, Ca(Ti 3+ ,Mg,Ti 4+ )AlSiO 6 with an end-member formula CaTi 3+ AlSiO 6 , is a new member of the Ca clinopyroxene group, where the trivalent cations are dominant in the M1 site with Ti 3+ being the dominant trivalent cation. It occurs as micrometer-sized crystals along with spinel and perovskite in a melilite host in Ca-,Al-rich refractory inclusions from the Allende meteorite. The mean chemical composition determined by electron microprobe analysis of the type material is (wt%) SiO 2 27.99, Al 2 O 3 24.71, CaO 24.58, Ti 2 O 3 10.91, TiO 2 6.68, MgO 4.45, Sc 2 O 3 0.43, V 2 O 3 0.19, ZrO 2 0.13, FeO 0.08, Cr 2 O 3 0.03, sum 100.20. Its empirical formula calculated on the basis of 6 O atoms is Ca 1.00 [(Ti 3+ 0.35 Al 0.18 Sc 0.01 V 3+ 0.01 ) Σ0.55 Mg 0.25 Ti 4+ 0.19 ] Σ1.00 (Si 1.07 Al 0.93 ) Σ2.00 O 6 . Grossmanite is monoclinic, C2/c; a = 9.80 Å, b = 8.85 Å, c = 5.36 Å, β = 105.62°, V = 447.70 Å 3 , and Z = 4. Its electron back-scatter diffraction pattern is an excellent match to that of Ti 3+ -rich pyroxene with the C2/c structure. The five strongest calculated X-ray powder diffraction lines are [d spacing in Å, (I), hkl] 2.996 (100) (2̅21), 2.964 (31) (310), 2.581 (42) (002), 2.600 (28) (1̅31), 2.535 (47) (221). The name is for Lawrence Grossman, a cosmochemist at the University of Chicago.
Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
