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The most common structure displayed on the etched surface of iron meteorites is a more or less fine intergrowth of kamacite and taenite lamellae that intersect one another at various angles. These fascinating patterns of crisscrossing bands and ribbons, called "Widmanstätten figures" for their discoverer, Alois von Widmanstätten, reveal an intergrowth of larger kamacite and taenite plates. This intergrowth has a spatial arrangement in the form of an octahedron, and thus, these iron meteorites are called octahedrites. Spaces between larger kamacite and taenite plates are often filled by a fine-grained mixture of kamacite and taenite called plessite, for the Greek word for "filling". The octahedrites are further divided into several subgroups based on the width of their kamacite lamellae, and each subgroup is associated with a particular chemical class of iron meteorites.