In his treatment of magic, Albert the Great was not guided by traditional biases. Important testimonies to that effect are found in his De mineralibus, one of his works on natural philosophical matters, which explained the allegedly magic ef fects of precious stones in terms of a systematically elaborated theory. Albert invoked in this context suitable metaphysical principles: the power of a particular stone (virtus lapidis) derives, according to his view, from its respective species and the forma substantialis associated with it. By thus integrating magical effects into the rational and conceptual framework of natural philosophy, the Dominican left the methods of other mineralogical authors far behind. The resulting demystification allowed the science of mineralogy to reach a new level of philosophical and scientific sophistication.