Abstract: Chloritic veins in serpentinite and their weathering products were analyzed by X-ray powder diffraction (XRD) and X-ray fluorescence spectrometry (XRF). Chlorite formed during the Hercynianage orogenesis had apparently been partly transformed to high-charge vermiculite during subsequent metamorphism of the rocks. The idealized structural formulae for these minerals are (Al_1.9Fe³⁺_0.2Fe²⁺_0.4Mg_9.2Cr_0.2)(Si^5.8Al_2.2)O²⁰(OH)₁₆ and X_1.3(Fe³⁺_0.7Fe²⁺_0.1Mg_5.2Ni_0.1)(Si_5.8Al_2.2)O₂₀(OH)₄, respectively. This transformation appears to have taken place by the removal of the hydroxy-interlayer from the chlorite without major effect on the rest of the structure. It is not clear whether other hydroxy-interlayered vermiculites containing less tetrahedral aluminum were intermediate weathering products or inherited minerals. The ultimate weathering product of chlorite and vermiculites was a Fe³⁺-rich smectite, which probably formed by precipitation from solution.