Specific gravity: 2.966 calculated
Streak: Very pale yellow
Colour: Light yellow to sulphuric yellow
Ježekite is a supergene, low-temperature mineral formed by
weathering of uraninite associated with post-mining processes
To date (October 2020) ježekite is known only from the type locality, the Geschieber vein, Svornost Mine, Jáchymov, Karlovy Vary District, Karlovy Vary Region, Czech Republic, as a crystalline crust of thin, bladed prismatic crystals of yellow to sulphuric yellow colour, associated with schröckingerite, gypsum, čejkaite and andersonite (Mindat, https://hal.archives-ouvertes.fr/hal-01575308). Ježekite was approved in 2014. It is a supergene, low-temperature mineral formed by hydration-oxidation weathering of uraninite associated with post-mining processes. It exhibits a bright greenish white fluorescence under both long-wave and short-wave UV (https://hal.archives-ouvertes.fr/hal-01575308).
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