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Formula: NaMn2+(Mn2+Fe3+)Fe3+2(PO4)4(OH)2.8H2O
Phosphate, jahnsite subgroup,
jahnsite group,
manganese-bearing mineral
Crystal System: Monoclinic
Specific gravity: 2.774 calculated from the empirical formula
Hardness: about 4
Streak: Pale yellow
Colour: Orange-yellow
Environments
Pegmatites
Metamorphic environments
Localities
The type locality, the Wiperaminga Hill West Quarry, Boolcoomatta Reserve, Olary Province, South Australia, is situated
in the mineralogically rich Curnamona Province, which has a long history of exploration and mining for base metals as
well as industrial minerals such as feldspar,
muscovite, beryl and
baryte. The geology comprises
greenschist to
granulite facies metasediments overlain by relatively
unaltered sediments and intruded by Mesoproterozoic (1,600 to 1,000 million years ago)
granitic sheets and
pegmatites. These are of the
beryl - columbite - phosphate -
rare-earth-element type. The Wiperaminga Hill pegmatites were
worked for feldspar, muscovite and
beryl.
Masses of primary
triplite were found on the dumps of the eastern quarry.
Secondary phosphate minerals developed through hydrothermal
alteration and weathering in an oxidising, low temperature, acid environment. The
triplite is mostly
manganese-dominant with compositions extending to
zwieselite, and
secondary minerals are
manganese- and iron-
rich.
Jahnsite-(NaMnMn) was found on the mine dumps in a single cavity in a matrix of
triplite, quartz,
fluorapatite, and minor pyrite.
Associated minerals are bermanite,
phosphosiderite, strengite,
and an unknown manganese-iron
phosphate.
Jahnsite-(NaMnMn) forms aggregates of twinned prismatic crystals with individual crystals up to 80 microns in
length and 25 microns across
(CJMP 61.6.1163-1173)
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