Home > American Minerals – March 20 > MS1306 Johannite

Johannite - Sold

Johannite is a copper uranium sulfate mineral, originally described from Jáchymov in the Czech Republic (Haidinger, 1830). The mineral name honors Austrian Archduke Johann Baptist Josef Fabian Sebastian (1782-1859), founder of the Landesmuseum, Graz, Austria. A crystal structure solution by Mereiter (1982) demonstrated eight molecules of water per formula unit in johannite, thus establishing the modern IMA formula.

Johannite here forms a druse of green microcrystals covering one surface of a sandstone matrix. The johannite forms blistering aggregates to 3 mm rising above the matrix, imparting a bit of relief to the specimen. There is a spot of yellow uranopilite in association. Formerly in the David P. Wilber collection. Rich example!