of these meteorites consists of the FeNi-alloys kamacite and taenite. Minor minerals, when occurring, often form rounded nodules of troilite or graphite, surrounded by schreibersite and cohenite. Schreibersite and troilite also occur as plate shaped inclusions, which show up on cut surfaces as cm-long and mm-thick lamellae. The troilite plates are called Reichenbach lamellae. The chemical composition is dominated by the elements Fe, Ni and Co, which make up more than 95%. Ni is always present; the concentration is nearly always higher than 5% and may be as high as about 25%. A significant percentage of nickel can be used in the field to distinguish meteoritic irons from man-made iron products, which usually contain lower amounts of Ni, but it is not enough to prove meteoritic origin. Use Iron meteorites were historically used for their meteoric iron, which was forged into cultural objects, tools or weapons. With the advent of smelting and the beginning of the Iron Age the importance of iron meteorites as a resource decreased, at least in those cultures that developed those techniques. In Ancient Egypt and other civilizations before the Iron Age, iron was as valuable as gold, since both came from meteorites, for example Tutankhamun's meteoric iron dagger. The Inuit used the Cape York meteorite for a much longer time. Iron meteorites themselves were sometimes used unaltered as collectibles or even religious symbols (e.g. Clackamas worshiping the Willamette meteorite). Today iron meteorites are prized collectibles for academic institutions and individuals. Some are also tourist attractions as in the case of the Hoba meteorite. Classification Two classifications are in use: the classic structural classification and the newer chemical classification. Structural classification The older structural classification is based on the presence or absence of the Widmanstätten pattern, which can be assessed from the appearance of polished cross-sections that have been etched with acid. This is connected with the relative abundance of nickel to iron. The categories are: Hexahedrites (H): low nickel, no Widmanstätten pattern, may present Neumann lines; Octahedrites (O): average to high nickel, Widmanstätten patterns, most common class. They can be further divided up on the basis of the width of the kamacite lamellae from coarsest to finest. Coarsest (Ogg): lamellae width > 3.3 mm Coarse (Og): lamellae width 1.3–3.3 mm Medium (Om): lamellae width 0.5–1.3 mm Fine (Of): lamellae width 0.2–0.5 mm Finest (Off): lamellae width < 0.2 mm Plessitic (Opl): a transitional structure between