page_title: Mining in the Upper Harz
section_title: Preparation of Upper Harz ore
hierarchical_section_title: Mining in the Upper Harz / Preparation of Upper Harz ore
caption_attribution_description: English: This image shows a stamp battery used in the former copperworks in Olbernhau-Grünthal in the Ore Mountains, Saxony, Germany. Deutsch: Das Bild zeigt ein Pochwerk der ehemaligen Saigerhütte Grünthal im Erzgebirge.
context_page_description: Mining in the Upper Harz region of central Germany was a major industry for several centuries, especially for the production of silver, lead, copper, and, latterly, zinc as well. Great wealth was accumulated from the mining of silver from the 16th to the 19th centuries, as well as from important technical inventions. The centre of the mining industry was the group of seven Upper Harz mining towns of Clausthal, Zellerfeld, Sankt Andreasberg, Wildemann, Grund, Lautenthal und Altenau.
context_section_description: The processing of minerals in the Upper Harz depended on the type of ore extracted. For example, the density of the Upper Harz lodes was very variable. Unlike the ore at Rammelsberg, the ore minerals were less intermingled with one another and the host rock. This enabled, from the beginning of mining operations in the Upper Harz, ore minerals to be processed into concentrations with a higher metal content than that of unroasted ore.
  In the Middle Ages until the start of the Early Modern Period the ore was broken up above ground using sledges and sorted by hand into silver, lead and copper ores and gangue. The pounding stones (Pochsteine) or stamps used have occasionally been found in recent times during archaeological excavations. The use of water power increased around the turn of the 16th and 17th centuries and it began to be employed in processing to enrich the ore concentration. On the one hand water was used as an energy source; on the other it was used to wash out the unwanted clay and to separate ore from gangue by making use of the different density of the minerals. The tailings from the washing process were simply emptied into the rivers of the Harz along with the used driving water. The low efficiency of the first ore processing machines resulted in a high content of heavy metals in the rivers. As a consequence of using the aforementioned water-based method of processing the stamp mills (Pochwerke) were located in the deeper river valleys. As a rule, they obtained water from the pits, where it had been used to drive water wheels and reversing wheels. Until the beginning of the industrial era, mechanical processing was carried out as follows:
  Coarse crushing with a heavy sledge (later with crushing machines).
  Wet screening in coarse sieves (trommels). The ore is washed (and gangue removed) and sorted by size.
  Manual separation (Handscheidung) of the coarse lumps of ore, pure ore minerals (so-called rough ores or Derberze) were sorted, dry crushed and went straight on sale (to the smelters). The work on the picking tables (Klaustischen) was carried out mainly by women, the elderly and youths.
  Washing (Siebwaschen) of the 'smalls' (Grubenkleins) or ore dust (Feinerze) in water-filled jigging tubs (Setzfässern). By dipping an ore-filled sieve several times in water the heavier pieces that were more ore-rich, settled in a lower layer. This process was later mechanised using jigging sieves (Setzmaschinen, not to be confused with the Setzmaschinen used in crushing).
  Wet stamping (Nasspochen) of ore which is more finely mixed with the gangue until it forms a 'sand'.
  Separation of the stamped ore on tables (Herdwäschen) using gravity. Depending on the design and drive mechanism, they were called vanners (Planherde), percussion tables (Stoßherde) or rotating tables (Rundherde). The fundamental principle was that heavy particles of ore remained on the table and the gangue would be washed away by water.
  The slimes or tailings from the preceding set of processes were further separated from the particles of ore in tyes (Schlammgräben) by sedimentation.
  The resulting concentrates (Schlieg or Schliech) were sold to the smelters. The preparation of the different types of ore was carried out as far as possible by visually sorting the concentrates by hand in order e.g. to separate out lead from copper concentrates.
  After 1850 the small and scattered stamp mills and ore washeries were replaced by central ore dressing plants. The basic steps - coarse crushing - manual separation - sieving - jigging - fine crushing - table work  and slime washing - remained much the same. The process was increasingly mechanised and perfected. In 1905 the most modern ore dressing plant in Germany went into operation in Clausthal using the gravity dressing process. It was located near the Ottiliae Shaft on the site of the old central ore processing plant of 1872. It employed up to 650 workers and processed all ore from the Clausthal and Zellerfeld pits until 1930. A change occurred in the 1920s with the introduction of the froth floatation in Bad Grun
caption: Stamp mill of the old Saiger works (Saigerhütte) of Olbernhau-Grünthal in the Ore Mountains
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