El acebo y el Rey sin fe

Research literature on the extraction of alum, the mineral salt basic to the economy of Christian Europe, entirely passes over the Iberian deposits in production between the fall of Constantinople and the commencement of the Papal operation at Tolfa in 1463. The sites of these are here identified, with an indication that their mineralogical formation is not that of the classic volcanic strata of Tuscany and Mazarrón. The much repeated theory on the way alum-bearing rock was located is shown to be suspect, and the pre-Mazarrón history of Spanish alum is given its context in the turbulent politics of the mid-century dynastic confrontations