Harz granite

Harz granite (German: Harzer Granit, pronounced [ˌhaːɐ̯tsɐ gʁaˈniːt]) is found in the Harz Mountains of central Germany. It may be divided into five types, all of which were widely used as natural stone: Knaupsholz granite, Birkenkopf granite, Wurmberg granite, Königskopf granite and Ilsestein granite. The first three granites were widely used in North Germany, Belgium and the Netherlands and, later, also in East Germany. Knaupsholz granite was "for a long time one of the most important types of cut stone in the former GDR".

In 2009 only Knaupsholz granite was still being quarried.

The granitic plutons of the Harz Mountains - the Brocken, Ramberg and Oker plutons - were formed at the end of the Harz mountain building period (the Hercynian orogeny) during the Late Carboniferous about 300 million years ago. These natural stones were formed when large magma intrusions in the Brocken granite massif solidified at different cooling and crystallization rates into several differently coloured granites. The Harz granites are part of the Brocken granite complex, which is the largest granite complex in the Harz with an area of 165 square kilometres (64 sq mi). The Harzburg gabbro-norite intrusion forms part of this complex, but has a primary chemistry similar to an island-arc tholeiite, although it shows the effects of large scale assimilation of crustal rocks.

Among the large quarrying concerns operating before the Second World War in 1938 were the firms of Zureck in Wernigerode (100 to 110 employees), Hannoversche Basaltwerke mbH with its branch, the Wernigerode Granite Quarries (Granitsteinbrüche Wernigerode, 60 to 70 employees), and Braunlager Granit- und Schotterwerke G.m.b.H. (45 employees). There were also 5 to 7 medium and 15 to 17 small businesses with a combined total of 600 employees. Their market at that time comprised the entire territory of the German Reich, Belgium and the Netherlands.

In 1948, after the war, 30 to 40 quarrymen were working in the Braunlager Granit- und Schotterwerken as well as an unknown number in another firm in Lower Saxony. There are no exact figures for the numbers of workers in the firms of the German Democratic Republic (GDR). The Knaupsholz and Birkenkopf quarries in the GDR and the divisions of the Zureck company in Wernigerode were expropriated on 5 November 1945.

In the early 1950s, the following quarries in the Brocken granite region were listed by Sickenberg (1951): Eckerloch, Schneeloch, Gebbertsberg, Wurmberg, Haserode, Wolfklippen, Großer und Kleiner Birkenkopf, Knaupsholz, Ottofels, Neustätter Hau, Forsthaus Plessenburg and Gelochter Stein. In 1958, eight quarries were still being worked in the territory of the GDR, but only two were left in 1969 (Knaupsholz and Birkenkopf).

Knaupsholz granite was quarried in the Knaupsholz forest district near the small settlements of Drei Annen Hohne and Schierke, a kilometre east of Schierke station in Saxony-Anhalt. Knaupsholz granite was one of the most important building stones in East Germany.

Knaupsholz granite is grey-red in colour and coarse-grained. It contains 33.5% quartz, 45.9% alkali feldspar, 15.1% plagioclase feldspar, 4.8% biotite and chlorite, 0.7% ore minerals, like magnetite, pyrite, hematite, and 0.7 others. The alkali feldspar crystals can be up to 18 mm across.