Klaus Müller/Bernd Ullrich:
The alumn slate mine "Morassina" near Schmiedefeld (Rennweg, Saalfelder Höhe) in the Thuringian Slate Mountains
The most important branch of the mining industry in the Schmiedefeld district (Thuringian Slate Mountains) was the iron ore mining, which probably already began in the 12th Century and was given up not before 1972 for profitability reasons. Alum slate mining in the location of "Morassina" was mentioned documentary for the first time in 1683. The mine was named after one of the owners, Leonard Morassi. After 177 years of mining usage the underground work was ceased in 1860. Since the year 1993 the "Morassina" is reopened as a technical monument for visitors. The goal of the mining industry was the extraction of alum slate for the production of iron and copper vitriol as well as alum. By-products were coloured clays (Thuringian Black or Brocken Black, Ochre, English-Red), sulfur, sulfuric acid (vitriol oil) and sulfur water. As the centuries went by, colourful secondary minerals were accumulated as products of the oxidative weathering of the sulfid minerals in the gotten. They took on the forms of dropstones, crusts on the alum slate and sludges which have been discovered during the reopening of the mine by the SDAG Wismut in 1951. These formations consist mainly of iron sulfate hydroxides, iron phosphate sulfates and iron phosphates.