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Formula: Pd3Ni4Te8
Telluride, palladium- and
nickel- bearing mineral
Crystal system: Tetragonal
Environments
Plutonic igneous environments
Metamorphic environments
Proxitwelvefoldite is a new mineral, approved in 2024 and to date (November 2025) reported only from the type
locality.
Natural quasicrystals, compounds with characteristics intermediate between crystalline material and glass, have been
so far discovered in extraterrestrial materials only. Furthermore, their occurrence in nature is limited to
metallic, aluminium-bearing alloys. The presence of metallic
aluminum in these minerals raised doubts about their potential occurrence
in terrestrial rocks. The geochemical conditions needed to form metallic
aluminium are so reducing that they are considered very unlikely in a
terrestrial environment.
The discovery of the first terrestrial approximant of a dodecagonal quasicrystal has been reported; it does not
contain aluminium. It is a Pd-Ni-telluride with formula
Pd3Ni4Te8 and tetragonal symmetry, which was found as small inclusions in a rock
sample from Kalgoorlie, Western Australia. Periodic approximants are crystalline materials that share a similar
chemical composition with quasicrystals but have a slightly altered atomic structure, aligning their symmetry with
the traditional principles of three-dimensional crystallography. These crystalline approximants provide insights
into the local atomic structure of their corresponding quasicrystals
(AM 110.4.650–654).
Localities
From the type locality, Kalgoorlie-Boulder, Kalgoorlie-Boulder Shire, Western Australia, Australia,
proxitwelvefoldite was discovered in a historic specimen in the Natural History Museum of the University of
Florence; it is very rare and occurs as micrometer-sized crystals associated with
iron-bearing melonite in a silicate
matrix composed of major chlorite and
lizardite. Its name indicates its pseudo-12-fold symmetry.
Proxitwelvefoldite is the first terrestrial pseudo-dodecagonal
quasicrystal approximant, a periodic
crystalline solid with a composition close to that of a quasicrystal,
and its existence suggests that a dodecagonal quasicrystal may exist in
the Pd-Ni-Te system. The find is significant because natural
quasicrystals have so far been described only from extraterrestrial
samples
(AM 110.5.830).
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