Iron meteorites come from the core of dead asteroids. Heavy metallic elements sank towards the center of these asteroids due to gravity. Collisions with other bodies then destroyed these asteroids, releasing their metallic cores to space. Iron meteorites are alloys, mainly of iron and nickel, although they also contain trace elements such as iridium. Iron meteorites account for only 4% of all observed meteorite falls, by number. However, due to their high density, the total weight of iron meteorites accounts for almost 50% of observed meteorite falls. This percentage increases up to 83% if the total weight of meteorite finds is included as well. Current scientific classification for iron meteorites is complex and exclusively dependent on the meteorite’s chemical composition. It includes 15 groups as follows: IAB, IC, IIAB, IIC, IID, IIE, IIF, IIG, IIIAB, IIICD, IIIE, IIIF, IVA, IVB, and Ungrouped irons. This classification is necessary for scientists as it is precise. There is a more visually intuitive classification that some collectors follow that is based on the internal structure. According to their structures, iron meteorites are classified into 3 types: octahedrites, hexahedrites and ataxites.