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Formula: PbMn2+2Fe3+2(PO4)3(OH)3
Phosphate, bjarebyite group,
manganese-bearing mineral
Crystal System: Monoclinic
Specific gravity: 4.416 calculated
Hardness: 4
Streak: Pale orange
Colour: Brownish orange
Environments
Plumboperloffite is a new mineral, approved in 2020 and to date reported only from the type locality.
Localities
At the type locality, the Wiperaminga Hill West Quarry, Boolcoomatta Reserve, Olary Province, South Australia,
pegmatites were exploited for
feldspar, beryl and
muscovite between 1957 and 1980. The
pegmatites occur near the base of a prominent range of hills
which comprise banded quartz–mica
gneiss and schist of the
Early to Middle Proterozoic age (2.5 to 1.0 billion years ago). The metasediments have been
granitised and in many places are intruded by
granite and associated
pegmatite and
aplite bodies. The
pegmatites are mineralogically zoned and comprise an outer
border zone of fine- to medium- grained microcline,
quartz, plagioclase and
muscovite, an intermediate zone of coarse-grained
muscovite, quartz,
microcline, plagioclase,
beryl and apatite (and
triplite), and an inner quartz core or
cores. The Wiperaminga Hill pegmatites belong to the
beryl –
columbite–phosphate rare element type. Phosphate minerals,
dufrénite, florencite,
apatite, triplite,
dickinsonite and barbosalite
have been reported from this locality.
In 2018 masses of orange to dark brown
triplite–zwieselite were found on
the dumps of the eastern quarry. Secondary phosphate minerals
have formed in seams and cavities in the
triplite–zwieselite by hydrothermal
alteration and weathering, in an oxidising, low temperature, low-pH (very acid) environment.
Plumboperloffite occurs in a single cavity in a matrix comprising
triplite, barbosalite and minor
quartz. Associated minerals are
fluorapatite,
phosphosiderite,
natrodufrénite and fluorite.
Plumboperloffite occurs as thin tabular to bladed vitreous crystals, with a brownish-orange colour. Individual
crystals are up to 40 μm in length
(MM 88.2.170–175).
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