An unique As-Bi association from Jachymov

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Created on Wednesday, 07 December 2016 20:14

Last Updated on Wednesday, 07 December 2016 20:28

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An unique As-Bi mineralization of the Geister vein in Jáchymov.

The Jáchymov ore area is typical by its occurrences of various secondaries of arsenic, uranium and other elements. Very popular are recently growth secondaries from dumps or directly from the old workings, originated during last tenths or hunderts years. In Jáchymov above the Rovnost I shaft occurred very rich association of supergenne minerals of As, P, Cu and U, which belongs among the most interesting in Czech Republic of its kind. The age of this mineral association is about several dozens of thousands or lower hundreds of thousands years.

The Geister vein belongs among the most rich veins in Jáchymov, it was mined from the 16th century. Nice ore lenses were found there, the last one was mined out in the half of the 19th century. Thanks to the collectors workings especially from the 1970s it was found interesting supergenne mineralization here, also known from the mining time in 19th century.

Brown to grey columnar walpurgite crystals associated with green tabular torbernite crystals. Jáchymov, Geister vein. FOV 4 mm.

Very typical and the most common is torbernite forming up to 1 cm large tabular crystals of emerald green colour. Common associated mineral is walpurgite forming columnar and tabular crystals of yellow, grey, green and brown colour. Some of its samples could belong to much rarer fosfowalpurgite, but it was not confirmed from there yet. 

Black to grey spherical eulytine aggregates (maybe in mixture with smrkovecite) growing together with yellow walpurgite. Jáchymov, Geister vein. FOV 4 mm.

Much rarer occurred black to grey eulytine aggregates up to 2 mm in diameter. Some layers in those aggregates could be represented by smrkovecite, which was confirmed by several point analyses only. Very common was locally mixite too forming up to 1 cm large massive aggregates comprised of thin needles.

Yellow-green columnar walpurgite crystals growing in quartz. Jáchymov, Geister vein, FOV 4 mm.

Rare spherical green to yellow aggregates of atelestite together with white churchite-Y aggregates.Jáchymov, Geister vein. FOV 3 mm.

Rarely was found atelestite surroundings up to several cm large aggregates of massive bismite. Atelestite formes up to 1 mm large spherical aggregates. Also churchite-Y was extremly rare in this association.

Research of this very interesting association from newly found historical samples will follow in the next year, so it will be possible to fill another information about. Some of described minerals, including walpurgite crystals, is possible to find rarely on the old workings dumps behind the Rovnost 1 shaft in the Adam shaft direction. Also the mrázekite aggregates belongs to this association, its photography will be possible to see in the outcoming publication about Jáchymov in the year 2017.