An alum plant was opened in the Saaletal as early as 1544. In 1546 an alum hut on the Wetzelstein was described by Georgius Agricola. According to Hieronymus Völker, these Fregian alum and vitriol plants were in the immediate vicinity of the Wetzelstein. This alum hut changed hands several times until it was acquired in 1760 by the important Leipzig banker and merchant Christian Gottlob Frege, the progenitor of one of the richest banking families of the time. The Frege family only continued the business until 1850, because after 1850, chemical extraction methods gradually replaced aluminum schist as a source of alums. The collapse of the mining facilities followed. In 1874, Dr. Richard Woldemar Frege, owner of a manor and professor at the Leipzig Faculty of Law and great-grandson of the progenitor Christian Gottlob Frege, an older property on the Wetzelstein. Here on the steep bank of the Saale, opposite the so-called Bohlenwand (today the NSG and National Geotope) in the district of Obernitz, he had Constantin Lipsius build a small castle in the Neo-Romanesque style from 1878 to 1880 using mighty sand and quarry stone blocks, which he including the property in 1913 bequeathed to his newly founded foundation, which was based in Abtnaundorf (Leipzig). Wikipedia