Most Common type of iron meteorite, composed mainly of taenite and kamacite and named for the octahedral (eight-sided) shape of the kamacite crystals. When sliced, polished and etched with an acid such as nitric acid, they display a characteristic Widmanstätten pattern. Spaces between larger kamacite and taenite plates are often filled by a fine-grained mixture of kamacite and taenite called plessite. Octahedrites are divided into several groups based on the width of their kamacite lamellae, and each subgroup is associated with a particular chemical class of iron meteorites. An etched slice of the IVA iron meteorite Gibeon is shown below.

Image source: Washington University – St. Louis
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