Ore genesis accumulation of hematite gravels called "pisolites" which form channel-iron deposits. These are preferred because they are cheap to mine. Lead-zinc deposits are generally accompanied by silver, hosted within the lead sulfide mineral galena or within the zinc sulfide mineral sphalerite. Lead and zinc deposits are formed by discharge of deep sedimentary brine onto the sea floor (termed "sedimentary exhalative" or SEDEX), or by replacement of limestone, in skarn deposits, some associated with submarine volcanoes (called volcanogenic massive sulfide ore deposits or VMS), or in the aureole of subvolcanic intrusions of granite. The vast majority of SEDEX lead and zinc deposits
Schlangenberg Nature Reserve the surface where erosion removed large amounts. About 200 million years ago aqueous metal solutions filled the cavernous rocks. Primary ores were created mostly consisting of Sphalerite, Marcasite and Galena. The process continued and the ore close to the surface decomposed due to the influence of carbon dioxide and water. In this process as a secondary ore calamine ZnCO which is known as calamine developed. Presumably the Celts had been the first digging for the calamine in the region. Ancient Celtic and Roman coins dated between 100 BC and 92/93 AD as well as remains of a Roman settlement proved