The false folklore believing in a gemstone made of frozen lynx urine was passed on into the Middle Ages. How do we (think we) know that Theophrastus was actually referring to tourmaline? Steven Watson puts it this way :
Modern consensus assigns the name lyngurium to some form of clear amber or else a type of tourmaline, given its yellow colour and well-known static elctrical properties, even though Theophrastus says it is like amber, implying that it is not amber, and despite the fact he discusses the two stones in two clearly distinct sections of De lapidibus. Such ‘rationalist’ attempt at identification need not concern us here, since our interest is not in what the stone lyngurium was, but, rather, how and why knowledge about it was transmitted from the classical world to the Middle Ages and Renaissance.
Being concerned what lyngurium was, most scientists stick with the alternate possibility. The alternative to ruled-out amber is tourmaline, based on the unusual properties (“unusual powers”) that Theophrastus attributed “his lynx-stone” with.
Keywords: geology, ethnomineralogy, gemstones, lapidary, folklore, misconception, knowledge transfer, philosophy.
References and more to explore
 Steven A. Walton: Theophrastus on Lyngurium: Medieval and Early Modern Lore from the Classical Lapidary Tradition. Annals of Science 2001, 58, pp. 357-379 [pennstate.academia.edu/StevenAWalton/Papers/576107/Theophrastus_on_lyngurium_Medieval_and_early_modern_lore_from_the_classical_lapidary_tradition].
 Darrell J. Henry and Barbara L. Dutrow: The Tourmaline Diaries. Natural History March 2012, 120 (3), 16-27.