Betpakdalite

minerals

scorodite

arsenic

gerdtremmelite

Formulae:
Betpakdalite-CaCa: [Ca2(H2O)17Ca(H2O)6][Mo6+8As5+2Fe3+3O36(OH)]
Betpakdalite-CaMg: [Ca2(H2O)17Mg(H2O)6][Mo6+8As5+2Fe3+3O36(OH)]
Betpakdalite-FeFe: [Fe3+2(H2O)15(OH)2Fe3+(H2O)6][Mo6+8As5+2Fe3+3O37]
Betpakdalite-NaCa: [Na2(H2O)17Ca(H2O)6][Mo6+8As5+2Fe3+3O34(OH)3]
Betpakdalite-NaNa: [Na2(H2O)16Na(H2O)6][Mo6+8As5+2Fe3+3O33(OH)4]
These are arsenic-bearing molybdates.

Specific gravity: 2.98 to 3.05
Hardness: 3 to 3½
Colour: Yellow
Environments

Hydrothermal environments

Localities

At its type locality, Mount Moliagul, Moliagul, Central Goldfields Shire, Victoria, Australia, betpakdalite-FeFe is associated with ferrimolybdite and muscovite as orange plates to 50 microns across in vugs in massive quartz veins (AJM 21.1.41).

The type locality for betpakdalite-NaNa is the Chuquicamata Mine, Chuquicamata District, Calama, El Loa Province, Antofagasta, Chile.

In quartz vein outcrops, in the Knöttel area, Krupka, Ústí nad Labem Region, Czech Republic, betpakdalite-CaCa occurs on vein quartz associated with molybdenite, molybdite and quartz (HOM).

The type locality for betpakdalite-NaCa is the Kyzylsai Mo-U deposit, Chu-Ili Mountains, Moiynkum, Jambyl Region, Kazakhstan.

At its type locality, the Kara-Oba W deposit, Betpakdala Desert, Karazhal, Karaganda Region, Kazakhstan, betpakdalite-CaCa occurs in quartz - hübnerite - pyrite - arsenopyrite veins in the oxidised zone, associated with ferrimolybdite, gypsum, jarosite, muscovite variety illite, limonite and opal (AM 47.172, HOM, Dana).

At its type locality, the Tsumeb Mine, Tsumeb, Oshikoto Region, Namibia, betpakdalite-CaMg crystals to 0.2 mm occur in a deep oxidation zone of a dolostone-hosted hydrothermal polymetallic ore deposit, singly or aggregated on scorodite and associated with chalcocite, digenite and quartz. It also occurs massive or as thin coatings, associated with hematite, quartz, scorodite, chalcocite, powellite, kaolinite, adamite, wulfenite, hidalgoite and gerdtremmelite (AM 70.1333, HOM, Dana).

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