Johannite

johannite

uraninite

marecottite

uranopilite

Images

Formula: Cu(UO2)2(SO4)2(OH)2.8H2O
Hydrated sulphate containing hydroxyl
Specific gravity: 3.32
Hardness: 2 to 2½
Streak: Pale green
Colour: Emerald-green, apple-green
Solubility: Decomposed by water, soluble in acids
RADIOACTIVE
Environments

Hydrothermal environments

Johannite is a rare secondary mineral in the oxidised portions of sulphide-bearing uraninite deposits, commonly of post-mine formation. Associated minerals include gypsum, zippeite, uranopilite, brochantite and chalcanthite (HOM).

Localities

The type locality is the Elias mine, Jáchymov, Karlovy Vary District, Karlovy Vary Region, Czech Republic.

At La Creusa Uranium prospect, La Creusaz, Les Marécottes, Salvan, Saint-Maurice, Valais, Switzerland, johannite is associated with marécottite (MinRec 35.4.358).

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