Johannite

johannite

uraninite

marecottite

uranopilite

Images

Formula: Cu(UO2)2(SO4)2(OH)2.8H2O
Hydrated sulphate, uranyl mineral
Crystal System: Triclinic
Specific gravity: 3.32 measured, 3.44 calculated
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.

Johannite from the Elias mine - Image

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

Johannite from La Creusaz - Image

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