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>Another issue of no less interest concerns the materials used in magical practices and sorcery. As far as the raw materials used are concerned, they must always be pure. Water, widely used in magic, must necessarily be treated, freshly collected from the source or river, and deposited in new containers that have not been used before. It was also common to use oil and honey in magical preparations, products considered pure due to their clear and transparent appearance; when land is used, it must be virgin land. The opposite occurred when the magical ritual was intended to cause harm to someone: in these cases, it was necessary to use cloudy water or earth collected from the roads. Precious stones were also given magical power and protective ability against various dangers, which for some authors could be related to the breastplate adorned with precious stones worn by the High Priest in the Temple of Jerusalem (Exodus, XXVIII, 17-20); this is how the ruby stone was considered linked to the figure of Ruben; it was taken as a protector against abortion and women's sterility; The emerald would be Levi's stone, giving him the ability to grant wisdom to a man and, in powder form, rejuvenate an old man; Topaz would be Simeon's stone, considered suitable for curing diseases, particularly eye diseases; the amethyst would be the stone of Gad, which was granted protection in battles, as well as in front of demons; and onyx would be the stone of Joseph, who was given the power to grant success in society
>All these practices, widespread at the end of the Middle Ages among Jews and spread among Christians through contact with Jewish communities, helped to propagate the idea of the Jew as a wizard and sorcerer
