The war had given the Silesian coal mines a new lease of life, as old seams once considered unsafe could now be worked by a ready supply of slaves, who could easily be replaced if killed or injured by pit collapses. IG Farben, the German pharmaceutical and chemical company, which was also partly involved in the manufacture of the Zyklon B gas-crystals used in the gas chambers, owned a majority stake in the mines. A major Third Reich contractor, IG Farben considered health and safety to be an irrelevance; at any cost, the coal was required to make synthetic rubber for the war effort. Adjacent to the mines, the Fürstengrube site comprised a series of smaller camps, all within a short distance of one another. Lager Süd (Southern Camp), run by the SS, was the only one for Jews, and held around 1,200 prisoners by the summer of 1943. Lager Waldek held non-Jewish prisoners of various nationalities, Lager Ostland was for female prisoners and Lager Nord for Russian POWs. Although all the camps came under jurisdiction of IG Farben, Lager Süd was the only section affiliated to Auschwitz. The prisoners were tasked to work the old mine (Altanlage) and excavate a new one (Neuanlage); in both cases, the working environment was appalling. Having been in Auschwitz for only a short time, Klein would not have had time to discover that living conditions in Lager Süd were every bit as harsh as the main Auschwitz camp. Coming from Terezín, where, despite the squalor, he at least lodged with members of his own family, and had some relative freedom, his new environment, with prisoners packed like proverbial sardines, and meagre food rations, was a living hell. Moreover, the camp contained what were known as Muselmänner, a slang word originating in Auschwitz, derived from ‘Muslim’, to denote prisoners who were exhausted, emaciated and ill: Muselmänner had difficulty standing upright, and so the image of a prone Muslim at prayer gave rise to the expression. The hard labour of twelve-hour shifts inflicted on the prisoners was not supported by adequate food, and anyone on a late shift would find their rations back at the camp to be cold, or having been bartered by other prisoners.