Ataxites are rare iron meteorites that lack the WidmanstŠtten Structure seen in octahedrites and the Neumann Lines seen in hexahedrites.  Ataxites are said to be internally structureless.  Cut & polished & nitric acid-etched surfaces of ataxites show a finely crystalline texture that would be described as aphanitic if it were a terrestrial igneous rock.


Compositionally, ataxites can be relatively rich in the mineral taenite (nickel-rich Fe-Ni alloy, with 27-65 wt.% nickel), or they can be finely crystalline mixes of taenite and kamacite (iron-rich Fe-Ni alloy, with ~5.5 wt.% nickel).



Ataxite (field of view ~2.5 cm across) - a cut, polished, nitric acid-etched surface of the Santiago Papasquiero Meteorite, found in 1958 in Durango, Mexico.  It consists of a finely crystalline mix of kamacite & taenite, plus other minor minerals.  Santiago Papasquiero is a strange ataxite that appears to be a completely metamorphosed and recrystallized octahedrite.  Most recrystallized octahedrites still retain vague hints of the original WidmanstŠtten structure.  This meteorite doesn't have any, so it isn't an octahedrite - it's an ataxite.

Published chemical info. indicates that Santiago Papasquiero has 7.5% nickel content overall.  The kamacite component has 6.8% Ni.  The taenite component has 30% Ni.

(More info. on the Santiago Papasquiero Meteorite)



Ataxite - weathered individual of the taenite-rich Chinga Ataxite from the Tannu Ola Mountains, Siberia, Russia.  The nickel content of this meteorite is 16.7%.  An associated impact crater is not yet known for this meteorite.  Chinga Meteorites have been exposed to Earth surface conditions for >2000 years.

(public display at meteorite museum at Odessa Impact Crater, Texas, USA)

(More info. on the Chinga Ataxite)



Some info. from:


Buchwald (1975) - Handbook of Iron Meteorites, Volume 3: 1080-1083.

Grokhovsky et al. (2000) - Mšssbauer spectroscopy of the Chinga Meteorite.  63rd Annual Meteoritical Society Meeting Abstracts.



Home page