Johann Karl Wilhelm Voigt
Johann Karl Wilhelm Voigt (20 February 1752 in Allstedt – 2 January 1821 in Ilmenau) was a German mineralogist and mining engineer. He initially studied law at the University of Jena, then in 1776 enrolled at the Mining Academy in Freiberg as a pupil of Abraham Gottlob Werner. He later relocated to Weimar, where in 1783 he was named secretary of the "Bergwerkskommission" (mining commission). During his time spent in Weimar he developed a close friendship with Johann Wolfgang von Goethe — through Voigt, Goethe received an education in mineralogy. From 1789 to 1821, he served as "Bergrath  (councillor of mines) in Ilmenau. He is best remembered for his dispute with Werner in regards to latter's theory of Neptunism; with Voigt maintaining that basalt was of volcanic origin. In 1800 he introduced the term lettenkohle" to describe coal with a large content of "letten" (regional German word for clay and mud). The thoroughfare "Bergrat-Voigt-Straße" in Erfurt commemorates his name.