Segers-Glocke, Christiane [Hrsg.]; Niedersächsisches Landesamt für Denkmalpflege [Hrsg.]; Institut für Denkmalpflege [Hrsg.]; Balck, Friedrich [Bearb.]: Arbeitshefte zur Denkmalpflege in Niedersachsen: Aspects of mining and smelting in the Upper Harz Mountains (up to the 13th/14th century) - in the early times of a developing European culture and economy (St. Katharinen: Scripta Mercaturae Verl., Heft 22.2000)

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The ore deposits of Rammelsberg were formed during the Mid-Devonian
period when metals dissolved in acidic hydrotherms were precipitated in contact
with seawater and deposited on the sea floor. The ores consists of sulphidic
minerals such as galena (PbS), sphalerite (ZnS), chalcopyrite (CuFeS2), pyrite
(FeS2) accompanied by barren accessories such as baryte (BaSO4), quartz (SiO2),
calcite (CaCO3) and shales (Fig. 3).
The extraction of copper was the primary aim of medieval mining at Ram-
melsberg. However, various ore minerals and dead rock are strongly intergrown
in this deposit and are not easily separated by mechanical means. Therefore, the
smelters were forced to smelt the whole ore including valueless and poisonous
components. Sphalerite containing cadmium for example was of no value to
medieval miners and smelters. Zinc has only been utilised since the middle of the
19th century. Correspondingly, we find a high concentration of zinc in slags from
medieval smelters of Rammelsberg ore.
The orebody of Rammelsberg shows broad compositional variations
throughout. Initially copper rich ores, low in lead and zinc, were mined. Water
prevented miners since the 12th century from reaching lower copper rich parts of
the deposit. This forced the miners to turn to parts of the deposit with lower
copper grades which had until then not been utilised.
The Rammelsberg ore deposit was one of the largest non-ferrous ore deposits
in the world. It has yielded a total of 1 300 0001 of lead, 700 000 t of zinc,
154 000 t of copper and 1 900 t of silver as well as many rare elements such as
gallium, gold, indium, tellurium, thallium etc. (KRAUME 1955). Mining at
Rammelsberg ended only in 1988 when the deposit had been exhausted.
Ore dykes of the Upper Harz
The ore dykes of the Upper Harz are situated in the western part of the Harz.
There we find 19 major fracture zones. Ore deposits along such fracture zones we
call ore dykes (cf. Fig. 7). These were presumably formed during the Cretaceous
and Tertiary periods when the most recent uplift of the Harz took place and
dissolved metals rising in acidic hydrotherms precipitated in the fractures (Fig. 4).
The ore deposits of the Upper Harz have been mined for more than 1700
years. The oldest written records referring to mining activities date from the 13th
century AD. The settlements in the Harz were formed as a direct consequence of
mining activities and are therefore situated in the immediate vicinity of former
ore dykes. Mining in the Upper Harz generally came to an end in the course of
the world-wide economic crisis of 1930. However, one mine remained in opera-
tion until 1992 when mining of the deposit was no longer economical.