Decagonite

decagonite

icosahedrite

khatyrkite

steinhardtite

Images

Formula: Al71Ni24Fe5
Alloy of aluminium, nickel and iron
Crystal System: Icosahedral
Colour: Grey to black
Environments

Meteorites

Decagonite is a natural quasicrystal phase, second to be discovered and approved after icosahedrite. See Mindat for a description of quasicrystals. Decagonite is a relatively new mineral, approved in 2015 and to date (February 2025) reported only from the type locality.

Localities

At the type locality, the Khatyrka meteorite, Iomrautvaam massif, Anadyrsky District, Chukotka Autonomous Okrug, Russia, decagonite was found as rare fragments up to ~60 microns across in one of the grains (labeled number 126) of the carbonaceous chondrite. The meteoritic grain contains evidence of a heterogeneous distribution of pressures and temperatures that occurred during impact shock, in which some portions of the meteorite reached at least 5 GPa and 1200°C. Decagonite is associated with aluminium-bearing trevorite, diopside, forsterite, ahrensite, clinoenstatite, nepheline, coesite, pentlandite, copper-bearing troilite, icosahedrite, khatyrkite, taenite, aluminium-bearing taenite and steinhardtite (AM 100.2340–2343).
Decagonite from the Khatyrka Meteorite - Image

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