Solid crystalline IM-10, and a process for its preparation

The invention concerns a crystalline solid, designated IM-10, which has the X ray diffraction diagram given below. Said solid has a chemical composition, expressed as the anhydrous base, in terms of moles of oxides, in accordance with the formula XO₂:mYO₂:pZ₂O₃:qR_2/nO:sF, in which R represents one or more cation(s) with valency n, X represents one or more tetravalent element(s) other than germanium, Y represents germanium, Z represents at least one trivalent element and F is fluorine.