The new mineral (IMA 2010–059) ernstburkeite, Mg(CH3SO3)2· 12H2O, occurs as solid inclusions, typically with a grain size up to 5 μm, in an ice core from the Dome Fuji station, East Antarctica. Due to the small crystal size most physical and optical properties cannot be established on natural material. Optically, the mineral is uniaxial (+), ω 1.402(1), ɛ 1.408(1) (589 nm), and nonpleochroic. Ernstburkeite is trigonal, space group R-3 (no. 148), a = 9.27150(8) Å, c = 21.1298(4) Å, V = 1572.99(4) Å3, Z= 3. Strongest X-ray powder-diffraction lines (relative intensities in parentheses) are: 7.04(42), 6.39(39), 4.64(100), 4.41(44), 3.87(89), 3.75(31), 3.74(35). The chemistry of the mineral in the ice core was confirmed by Raman microspectroscopy. The name is for Ernst A J. Burke, Belgian-born mineralogist at the Vrije Universiteit Amsterdam, Netherlands (1966–2005), chairman of the IMA Working Group on Inclusions in Minerals (1994–1998) and chairman of the IMA Commission on New Minerals, Nomenclature and Classification (2003–2008).