Two new alkali rare earth silicate fluorides have been synthesized as single crystals in a molten eutectic flux, RbCl/HRbF2. Rb3Sc2[Si4O12]F crystallizes in a novel structure type with the orthorhombic, noncentrosymmetric space group Pna 2 1 and lattice parameters a = 18.5645(13) & Aring;, b = 6.7591(4) & Aring;, and c = 10.4217(7) & Aring;. Rb2Sm[Si4O10]F forms as a distortion of the known A2Ln[Si4O10]F structure, crystallizing in the monoclinic space group P 2 1 / m , with lattice parameters a = 8.0886 (2) & Aring;, b = 8.8000(3) & Aring;, c = 8.2285(3) & Aring;, and beta = 90.2350(10)degrees. The syntheses and structures of these two compositions are discussed as well as the optical behavior of the Eu-doped Rb3[Sc1.9Eu0.1][Si4O12]F.