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Formula: Pd2Sb
Alloy of palladium and antimony,
platinum group mineral
Crystal System: Orthorhombic
Specific gravity: 10.694 calculated
Hardness: 4 to 5
Colour: Creamy white
Environments
Metamorphic environments
Hydrothermal environments
Naldrettite has been found in several different environments:
In magmatic
nickel - copper -
platinum group element
sulphide deposits.
In hydrothermal veins in porphyry
coppers of the
copper-gold type.
In platinum group element deposits of Alaskan-type zoned intrusions.
Occasionally in metasomatic
antimony-arsenic sulphide ore.
Occasionally in metamorphic nickel–oxide ore.
Occasionally in podiform chromitites.
Naldrettite can form in a variety of igneous rocks, even involving minimal concentrations of
palladium and antimony
(CM 59.6.1801-1820).
Localities
At the Luanga complex, Carajás mineral province, Pará, Brazil, a new (2021) find of naldrettite occurs in a
chromitite sample collected in the layered intrusion. Paragenetic
association with alteration assemblages (ferrian chromite,
iron hydroxides, chlorite) suggests
precipitation of naldrettite from metamorphic hydrothermal fluids.
The average composition of the sample shows major substitution of platinum
and arsenic. These elements were derived from the breakdown of
primary sperrylite,
and were incorporated in naldrettite deposited by percolating fluids, at temperature below 350°C.
Crystallisation of naldrettite generally occurs in the post-magmatic stage due to the activity of hydrothermal
fluids containing volatile species antimony,
arsenic, bismuth,
tellurium and palladium
(CM 59.6.1801-1820).
At the type locality, the Mesamax Northwest deposit, Ungava Peninsula, Nunavik, Nord-du-Québec, Québec, Canada,
naldrettite was found in 2005 associated with monoclinic pyrrhotite,
pentlandite, chalcopyrite,
galena, sphalerite,
cobaltite, clinochlore,
magnetite, sudburyite,
electrum and altaite. Other rarer
associates include ungavaite,
sperrylite, michenerite,
petzite and hessite.
Naldrettite occurs as anhedral grains, which are commonly attached or moulded to sulphide minerals, and also
associated with clinochlore. Grains of naldrettite vary in size
from ~10 to 239 μm. Naldrettite appears bright creamy white in association with
pentlandite, pyrrhotite,
clinochlore and chalcopyrite
(MM 69.89-97).
The naldrettite was found in a drill core through the contact zone between massive and disseminated sulphide
mineralisation hosted by amphibolite and
serpentinite replacing
pyroxenite and
peridotite
(HOM).
At the Noril'sk I intrusive, Medvezhyi Ruchei Mine, Noril'sk-1 Cu-Ni deposit, Noril'sk Cu-Ni deposit, Noril'sk,
Putoran Plateau, Taimyr Peninsula, Taymyrskiy Autonomous Okrug, Krasnoyarsk Krai, Russia, samples were collected from
exploration boreholes. In one of these samples arsenic-bearing
mertieite-II,
stibiopalladinite and possibly
norilskite, occur in the upper part of the
picritic
gabbro-dolerite.
Naldrettite, atokite,
kotulskite,
palladoarsenide, moncheite
and paolovite occur in association with numerous phases dominated by
arsenic compositions below the section
(CM 59.1437-1451).
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