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Slate deposits of the Harz Mountains [Germany]
The roofing slates of the Harz mountains are related to the Middle-Devonian 'Wissenbacher Schiefer' and were mainly mined above ground in the 'Oberharzer Devonsattel' southwest of Goslar. The 'Oberharzer Devonsattel' consist of Devonian units and generally shows a NW-vergency and NE-SW striking fold style. The deformation style is characterised by flexural shear folding with a following origin of a fanning fracture cleavage. The cleavage planes were partly deformed and thus built a kind of a fault plane (Plessmann & Wunderlich, 1961 in Mohr, 1993). The 'Wissenbacher Schiefer' is a slate with a well developed fanning fracture cleavage leading to thin splitting roofing slates. In some parts higher amounts of silty components and partly thin calcareous layers and lenselike calcareous intercalations can be observed. The colour is dark-blue grey and the old roofs in Goslar show the high lifetime and durability of the slate.
Slate districts in Harz mountains.
The slate mining of the Harz began very early and possibly started at the beginning of the 11th century and proven in the 13th century. Besides the usage for roofing, slate was also used for tables, flooring etc. Since 1963 slate was used for grit and as filling material for the concrete industry but the whole slate industry came to a standstill in 1975 (Stoppel, 2002).
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