We report on the crystal structure of a new polymorph of Li2FeSiO4 (prepared by annealing under argon at 900 degrees C and quenching to 25 degrees C) characterized by electron microscopy and powder X-ray and neutron diffraction. The crystal structure of Li2FeSiO4 quenched from 900 degrees C is isostructural with Li2CdSiO4, described in the space group Pmnb with lattice parameters a=6.2836(1) angstrom, b = 10.6572(1) angstrom, and c = 5.0386(1) angstrom. A close comparison is made with the structure of Li2FeSiO4 quenched from 700 degrees C, published recently by Nishimura et al. (J. Am. Chem. Soc. 2008, 130, 13212). The two polymorphs differ mainly on the respective orientations and alternate sequences of corner-sharing FeO4 and SiO4 tetrahedra.