The ab initio crystal structure solution of a layer silicate is presented. Since the crystallinity of the material is limited, the corresponding X-ray powder pattern shows only moderate resolution. Based on a new interpretation of the tangent formula, a general direct method strategy for the determination of the crystal structure of poorly crystalline materials from X-ray powder patterns is presented. The structure model derived from the interpretation of the E map was subsequently refined with the Rietveld technique using the whole diffraction pattern. This leads finally to a picture of the crystal structure of atomic resolution which explains in full detail the specific characteristics of the material.