Why is Alum an Alum?

Although the name Hanušovická vrchovina extends somewhere around Hanušovice, in reality it is even more extensive and actually forms the southern foothills of the highest Moravian mountains, Hrubé Jeseník and Králické Sněžník. The foothills are vast and at the same time quite high, they are actually almost mountains (category of middle mountains), although only one peak ranks them there, namely Jeřáb with a height of 1003 m.
The highest part of Hanušovická…