text: In 1886, Winkler was provided with a new mineral from the Himmelsfürst mine near Freiberg. The mineral, called argyrodite, was found by chemists to contain silver and sulfur.  When Winkler subsequently analyzed the mineral, he found that the individual components only added up to about 93&ndash;94% of its total mass, leading him to suspect that a new and previously unknown element must be present. After additional chemical purification steps over several months, Winkler isolated the pure element, germanium, on February 6, 1886 and published his results. The mineral argyrodite that was Winkler's start toward finding germanium is now known to be a double sulfide with formula GeS · 4AgS.
  To place germanium into the periodic table, Mendeleev suggested that it might be ekacadmium, an element he had predicted earlier.  In contrast, Lothar Meyer favored an identification of germanium with ekasilicon, a different predicted element.  Winkler isolated more of the pure material, and eventually obtained enough to measure some of its physical and chemical properties.  His results showed unequivocally that Meyers interpretation was the correct one and that nearly all of the new elements properties matched Mendeleev predictions. The close match between what had been predicted for ekasilicon and what was found for germanium was clear evidence for the utility and power of the periodic table and the concept of periodicity.