Liebermannite, KAlSi3O8, a new shock-metamorphic, high-pressure mineral from the Zagami Martian meteorite


Ma C1, Tschauner O2, Beckett JR1, Rossman GR1, Prescher C3, Prakapenka VB3, McDowell A4

1Division of Geological and Planetary Sciences, California Institute of Technology
Pasadena, California 91125, USA

2High Pressure Science and Engineering Center and Department of Geoscience
University of Nevada, Las Vegas, Nevada 89154, USA

3Center of Advanced Radiation Sources, GSECARS, The University of Chicago, Chicago, Illinois 60632, USA

4Advanced Light Source, ESG, Lawrence Berkeley National Laboratory
Berkeley, California 94720, USA




abstract

Liebermannite (IMA 2013-128), KAlSi3O8 with a tetragonal hollandite-type structure, is a new shock-generated high-pressure mineral from the Zagami meteorite, a basaltic shergottite from Mars. The space group is I4/m with Z = 2 and cell dimensions a = 9.140(36) , c = 2.736(21) , V = 228.56(25) 3 for the type material. The mean composition of the type example is (wt%) SiO2 65.4, Al2O3 19.0, K2O 13.02, Na2O 1.62, and CaO 0.37 (total 99.4), giving rise to an empirical formula of (K0.76Na0.14Ca0.02)Al1.03Si3.00O8.  Using this composition and the measured cell parameters leads to a calculated density of 3.98 g/cm3.  The Mohs hardness is estimated to be 6 - 7 . Liebermannite in Zagami likely formed via solid-state transformation of primary igneous K-feldspar during an impact event that achieved pressures of ~20 GPa or more. The mineral name is in honor of Robert C. Liebermann, a high-pressure mineral physicist at Stony Brook University, New York, USA.