ataxite

thumb|The Santiago Papasquiero meteorite, an ataxite 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. Field of view ~2.5 cm across. This is a cut, polished, nitric acid-etched surface. ]] Ataxites (from Greek meaning "without structure") are a structural class of iron meteorites with a high nickel content and show no Widmanstätten patterns upon etching.

==Characteristics== Ataxites are composed mainly of meteoric iron, a native metal found in meteorites that consists of the mineral taenite with minor amounts of plessite, troilite, and microscopic lamellae of kamacite. Ataxites are the most nickel-rich meteorites known; they usually contain over 18% nickel. The high nickel content is the reason that they do not develop a Widmanstätten structure, because in this case kamacite can be exsolved from taenite only at such a low temperature (below about 600°C) where diffusion is already too slow.