"The outstanding work that Fabian Käs has done so far on the difficult and intriguing subject of Arabic mineralogy will hopefully redraw attention to this somewhat neglected but no less important field of research; and together with the recent study of al-Tīfāshī’s stone-book by Armin Schopen and Karl W. Strauß, it might even pave the way for other scholars to arrive at a deeper understanding of the multifaceted world which medieval mineralogy evokes. The book reviewed here is, in any case, a stunningly flawless achievement."Oliver Kahl in Journal of Semitic Studies, vol 61, no 2, October 2016.