Images
Formula: Bi2Fe3+(Co,Fe3+)(AsO4)2(O,OH)4
Arsenate, bismuth- and
cobalt- bearing mineral
Crystal System: Triclinic
Specific gravity: 5.81 calculated
Hardness: 4½
Streak: Light brown
Colour: Brown, red-brown
Luminescence: Not fluorescent under long wave or short wave UV
Solubility: Completely soluble in warm, dilute hydrochloric acid without effervescence
Environments
Localities
At the type locality, the Güldener Falk Mine, Neustädtel, Schneeberg, Erzgebirgskreis, Saxony, Germany,
neustädtelite and cobaltneustädtelite were found at the mine
dumps. Further occurrences for neustädtelite and
cobaltneustädtelite are at other mine dumps in the vicinity of Schneeberg-Neustädtel, all are located within an
area of a few square kilometers. The specimens containing neustädtelite
and cobaltneustädtelite consist mainly of coarse quartz and
neustädtelite and cobaltneustädtelite crystallised in small vugs
in association with preisingerite, powdery
limonite/goethite, and rarely with
mixite, zeunerite, and
bismutite. The joint occurrence of
neustädtelite and cobaltneustädtelite together with
preisingerite seems to be a characteristic feature.
Preisingerite forms tiny lustrous nodular aggregates as well as dull,
seemingly decomposed, but still crystalline, masses and aggregates. These crystalline masses are frequently overgrown
by well developed neustädtelite and cobaltneustädtelite crystals.
Neustädtelite and cobaltneustädteliteusually form crystal
aggregates up to 0.3 mm in size and very small tabular crystals, mostly less than 0.1 mm; one sample of
cobaltneustädtelite exhibits crystals up to 0.2 mm across and 0.1 mm thick. The crystals are transparent to
translucent, and they have a brown colour and a light brown streak with an adamantine lustre
(AM 87.5.726-738).
Cobaltneustädtelite from the Güldener Falk Mine -
Image
Back to Minerals