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American Mineralogist

Journal of Earth and Planetary Materials

Ed. by Baker, Don / Xu, Hongwu / Swainson, Ian

IMPACT FACTOR 2018: 2.631

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Volume 102, Issue 7


Addibischoffite, Ca2Al6Al6O20, a new calcium aluminate mineral from the Acfer 214 CH carbonaceous chondrite: A new refractory phase from the solar nebula

Chi Ma
  • Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California 91125, U.S.A.
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/ Alexander N. Krot
  • Hawai’i Institute of Geophysics and Planetology, University of Hawai’i at Mānoa, Honolulu, Hawai’i 96822, U.S.A.
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/ Kazuhide Nagashima
  • Hawai’i Institute of Geophysics and Planetology, University of Hawai’i at Mānoa, Honolulu, Hawai’i 96822, U.S.A.
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Published Online: 2017-07-17 | DOI: https://doi.org/10.2138/am-2017-6032


Addibischoffite (IMA 2015-006), Ca2Al6Al6O20, is a new calcium aluminate mineral that occurs with hibonite, perovskite, kushiroite, Ti-kushiroite, spinel, melilite, anorthite, and FeNi-metal in the core of a Ca-Al-rich inclusion (CAI) in the Acfer 214 CH3 carbonaceous chondrite. The mean chemical composition of type addibischoffite measured by electron probe microanalysis is (wt%)Al2O3 44.63, CaO 15.36, SiO2 14.62, V2O3 10.64, MgO 9.13,Ti2O3 4.70, FeO 0.46 total 99.55, giving rise to an empirical formula of (Ca2.00)(Al2.55Mg1.73V1.083+Ti0.503+Ca0.09Fe0.052+)6.01(Al4.14Si1.86)O20.The general formula is Ca2(Al,Mg,V,Ti)6(Al,Si)6O20. The end-member formula is Ca2Al6Al6O20. Addibischoffite has the P1 aenigmatite structure with a =10.367 Å, b =10.756 Å, c = 8.895 Å, α =106.0°, β = 96.0°, γ =124.7°, V = 739.7 Å3, and Z = 2, as revealed by electron backscatter diffraction. The calculated density using the measured composition is 3.41 g/cm3. Addibischoffite is a new member of the warkite (Ca2Sc6Al6O20) group and a new refractory phase formed in the solar nebula, most likely as a result of crystallization from an 16O-rich Ca, Al-rich melt under high-temperature (~1575 °C) and low-pressure (~10−4 to 10−5 bar) conditions in the CAI-forming region near the protosun, providing a new puzzle piece toward understanding the details of nebular processes. The name is in honor of Addi Bischoff, cosmochemist at University of Münster, Germany, for his many contributions to research on mineralogy of carbonaceous chondrites, including CAIs in CH chondrites.

Keywords: Addibischoffite; Ca2Al6Al6O20; new mineral; warkite group; refractory phase; Ca-Al- rich inclusion; Acfer 214 meteorite; CH3 carbonaceous chondrite

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About the article

Received: 2016-11-28

Accepted: 2017-03-23

Published Online: 2017-07-17

Published in Print: 2017-07-26

Citation Information: American Mineralogist, Volume 102, Issue 7, Pages 1556–1560, ISSN (Online) 1945-3027, ISSN (Print) 0003-004X, DOI: https://doi.org/10.2138/am-2017-6032.

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© 2017 by Walter de Gruyter Berlin/Boston.

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