My PhD project explores Goethe’s writings on geology from the perspective of the interplay between materiality and immateriality. Specifically, I posit that Goethe’s descriptions of mountains, mines and rocks focus in equal part on the material and immaterial characteristics of the object in question, without privileging one or the other. Drawing on Goethe’s presentation of the role of the imagination in geological enquiry, his belief in the existence of generative forces within geological masses and his colour theory, inter alia, I demonstrate that Goethe’s geological writings are shaped by the monist duality of (im)materiality. I explore this hypothesis with reference to Goethe’s engagement with the project to reopen the mine at Ilmenau, which was a deeply formative experience for the development of his geological theories. My thesis makes a contribution to two separate fields of enquiry. Firstly, within the sphere of Goethe studies, it sheds light on Goethe’s geological work in general, which has been greatly under-researched compared to his endeavours in other scientific fields. In so doing, it also seeks to being together the arguments pursued by many critics to date, who have primarily focused on either the material or the immaterial in Goethe’s work, without attempting to create a synthesis of both. Secondly, it also represents a new avenue of enquiry for the burgeoning field of immateriality studies, which has primarily focused on disciplines such as anthropology and archaeology to date. In light of Goethe’s explicit emphasis on holism in his studies of the natural sciences, I contend that research on his geological writings (and, indeed, on the rest of his scientific output) should approach questions of materiality and immateriality with an eye to the same holism. In so doing, this paints a detailed picture both of Goethe’s engagement with the issue of (im)materiality and of his understanding of the geological world.