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

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) Å, c = 2.736(21) Å, V = 228.56(25) ų 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 (K_0.76Na_0.14Ca_0.02)Al_1.03Si_3.00O₈.  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 ½ - 7 ½. 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.