Two stages of skarn formation two tin enrichments : the Hämmerlein polymetallic skarn deposit western Erzgebirge Germany Skarn deposits are found on every continents and were formed at different times from Precambrian to Tertiary. Typically the formation of a skarn is induced by a granitic intrusion in carbonates rich sedimentary rocks. During contact metamorphism fluids derived from the granite interact with the sedimentary host rocks which results in the formation of calc silicate minerals at the expense of carbonates. Those newly formed minerals generally develop in a metamorphic zoned aureole with garnet in the proximal and pyroxene in the distal zone. Ore elements contained in magmatic fluids are precipitated due to the change in fluid composition. The temperature decrease of the entire system due to the cooling of magmatic fluids and the entering of meteoric water allows retrogression of some prograde minerals. The Hämmerlein skarn deposit has a multi stage history with a skarn formation during regional metamorphism and a retrogression of primary skarn minerals during the granitic intrusion. Tin was mobilized during both events. ...