Gerdtremmelite

gerdtremmelite

betpakdalite

scorodite

wilhelmkleinite

Images

Formula: ZnAl2(AsO4)(OH)5
Anhydrous arsenate containing hydroxyl
Crystal System: Triclinic
Specific gravity: 3.66 calculated
Streak: White
Colour: Yellowish brown to dark brown
Solubility: Insoluble in hydrochloric acid
Environments

Hydrothermal environments

gerdtremmelite is a very rare secondary mineral that to date (November 2021) has been reported only from the type locality.

Localities

At the type locality, the Tsumeb Mine, Tsumeb, Oshikoto Region, Namibia, gerdtremmelite occurs as a secondary phase in deeply oxidised ore specimens in the dolostone-hosted hydrothermal polymetallic ore deposit. It forms spherulitic aggregates of tabular crystals up to 3 microns in size and approximately 1 micron in length. Associated minerals include hematite, quartz, scorodite, powellite, betpakdalite, kaolinite, wilhelmkleinite and adamite (AM 71.845-847, HOM).

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