Gur, Ghur, Guhr or Bur? The quest for a metalliferous prime matter in early modern times.

It has been traditionally held that the idea of a prime matter of metals was abandoned in the eighteenth century, especially after the failure of Hermann Boerhaave to find it in mercury. However, documents tell a different story: the search for the metalliferous principle, in the form of an odd substance known as Gur, Guhr, Ghur or Bur, was very much alive in the 1700s. This was a project that involved Boerhaave himself, as is shown by his correspondence with J.B. Bassand. The first mention of this strange material appears in Sarepta, a collection of sermons by the sixteenth-century Bohemian preacher Johannes Mathesius, sometimes mentioned in the specialized literature but rarely studied. This paper discusses the various conceptions of this material held as the prime matter of metals, from Mathesius to the eighteenth century, involving reputed authors such as John Webster, Jan B. van Helmont, Georg E. Stahl and Boerhaave. [ABSTRACT FROM PUBLISHER]