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Formula: Na3CaMg11(PO4)9
Anhydrous phosphate, fillowite group
Stornesite-(Y) is an yttrium-bearing variety of chladniite
Crystal System: Trigonal
Specific gravity: 3.017 calculated
Hardness: 4½ to 5
Streak: White
Colour: Colourless
Common impurities: Fe,Mn,Si
Environments
Localities
At the Graves Nunataks 12510 meteorite, Graves Nunataks meteorites, Wisconsin Range, Eastern Antarctica, Antarctica,
the first widespread occurrence of rare chladniite was observed in the primitive
achondrite. Numerous 1 to 500 µm chladniite grains
were found, often on the margins between silicate clasts and the kamacite
portions of the large metal veins that permeated through the sample. The largest chladniite grains are
associated with merrillite,
kamacite, taenite,
troilite, albite,
forsterite, diopside and
enstatite, with a few tiny chladniite grains and an
apatite grain enclosed within
merrillite.
Meteoritic chladniite likely formed through oxidation of
schreibersite, scavenging Na from
albite, Ca from diopside, Mg from
enstatite/forsterite, Fe from
kamacite/taenite, and Mn from
alabandite/chromite when
available
(AM 109.1513–1522).
The Graves Nunataks 95209 meteorite, Graves Nunataks meteorites, Wisconsin Range, Eastern Antarctica, Antarctica,
is a primitive achondrite. Numerous grains of an
orthophosphate intermediate in composition between farringtonite and
graftonite/sarcopside are
found in association with iron- and
manganese- rich chladniite. The chladniite probably formed
both through replacement of magnesium-rich
graftonite and directly by reaction of metal with silicates, including
plagioclase. Apatite appears
to have played only a minor role in the formation of these phosphates
(AM 84.1354-1359).
At the Tablada I pegmatite, Parroquia District, Pocho Department, Córdoba Province, Argentina, chladniite,
previously found only in meteorites, was identified in the
pegmatite as inclusions in
beusite.
The refined crystal structure of pegmatitic
chladniite differs from the meteoritic one in the
cation ordering (Mg, Fe + Mn and Ca) at the various metal sites, with Mn being dominant at the M(1) position
(EJM 29.2.287–293). Hence it may be that this is not a true chladniite.
At the type locality, the Carlton meteorite, Carlton, Hamilton County, Texas, USA, a single grain of
chladniite was identified in a polished section of the iron
meteorite. The chladniite occurs within and near the
edge of a silicate-bearing inclusion that is approximately 5 x 5 mm2 in size.
Chlorapatite is the dominant mineral in the inclusion;
olivine, pyroxene and
plagioclase occur as mono or polymineralic clusters within
chlorapatite and along the outer portions of the inclusion.
Schreibersite occurs as millimeter-sized grains, and an intergrowth
of micron-sized Fe, Ni and FeS occurs as millimeter-sized pockets at the edges of the inclusion; the entire
inclusion is rimmed by kamacite.
Chladniite occurs as a single grain, which measures 175 x 975 µ2. Irregular fractures are filled
with hydrated iron oxides of terrestrial origin
(AM 79.375-380).
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