Greenish variety of muscovite, high in chromium (trivalent Cr replaces Al in the crystal structure). Note that trivalent V can also cause a greenish colour in muscovite (cf. roscoelite). Originally reported from Schwarzenstein Mt., Zemmgrund, Ziller valley, North Tyrol, Tyrol, Austria.
Named in 1842 by Karl F. Emil von Schafhäutl in honor of Johann Nepomuk von Fuchs [May 15, 1774 Mattenzell, near Bremberg, Lower Bavaria, Germany - March 5, 1856 Munich, Germany] professor of chemistry and mineralogy at University of Landshut and curator of the mineralogy collection.
Formula: K(Al,Cr)3Si3O10(OH)2 Elements listed: Al, Cr, H, K, O, Si
Chrome-mica, Chromian Muscovite, Chrommuscovite, and Gaebhardite