Famous Harz mine “Einheit / Drei Kronen und Ehrt“ New book in progress

 

A new and well illustrated mining book written by a team of 17 experienced authors will be on the market in September 2016 under the title „Einheit Mine – Golden Treasure of the Harz". Register now without obligation to get the information in time when and where to get the book.

 

Drei Kronen und Ehrt is a former visitor mine in active use until 1990. During the time of active minig, the pit was called Einheit. Stratigraphically, the place belongs to the geological unit Elbingerode Complex. The Volcanic-hosted massive sulphide mineralization at the Einheit deposit in the Harz Massif as part of the German Variscan is one of only two occurences of this mineralization type in Germany. It is associated with Middle Devonian acid volcanics in sequences. The mineralization consists almost entirely of pyrite, and was exploited as a sulphur-source for manufacturing acid.

 

Mining of the iron ores of the Elbingerode Complex is documented back into the 10th century, new archaeological findings even give hints on iron smelting in the 4th century. The earliest document mentioning the sources of the “Great Graben” originates from 1582. At this time the primary pyrite ores have probably already been discovered after centuries of mining of the overlaying gossan. In the 18th and 19th century the mining was transferred completely to underground work at up to 328 single collieries.

 

The most successful mining period in the Elbingerode Complex began after World War II. The three mines Büchenberg, Braunesumpf and Einheit delivered iron ores during this period till 1970. After this, only “Grube Einheit” continued mining of the massive sulfides for further 20 years. The peak level of production was reached in the early 1970s with 381.144 t/year raw material and 56.559 t/year sulfur content. In 1990 the production ceased because it was no longer economic. During the time of activity, about 13 Mt pyrite-rich material were raised from this mine; the sulfides from the whole Elbingerode Complex contained 50 Mt Fe.

 

This stratigraphic unit hosts some of the most important ore deposits in the Harz Mts. Over centuries the mining of iron ores has been of economical importance for the region, while today the recovery of Devonian limestones dominates.

 

The Elbingerode Complex consists of volcanics and reef carbonates, which are framed by shales and greywackes. The foot wall are the Wissenbacher Shales. In Middle Devonian, the magmatic activity of the early Variscan orogeny was initiated and submarine volcanic outflows developed along NE-SW striking crack systems. The bulky volcanic series of acid and basic rocks was deposited during three main phases. The ore horizon is located in the upper part of these series above trachitic lavas. These differ in color from light green-grey to violet-grey, which indicates a changing redox potential. Between the phases of volcanic activity and after its extinction, large reef carbonate complexes developed to a maximum thickness of about 600 m. The growth of the reefs ended in the Upper Devonian. During further geological history, the volcanics-reef-complex in the sedimentary trough was covered by shales and greywackes. The Variscan orogeny (Upper Devonian to Carboniferous) deformed the thick sedimentary layers together with the reefstones and volcanics into a disharmonic fold pattern. Further tectonics occurred during the Mesozoic, followed by elevation and erosion.