All structural classes of iron meteorites are found in this group but especially the medium and large crystal Octahedrites (Om-Og).
Silicate rich iron meteorites that are seemingly closely related to a rare group of Achondrites, the Winonaites, are also found in this group. Possibly the Winonaites and IAB iron meteorites derive from the same parent body.
IAB group meteorites frequently have bronze colored Troilite (iron sulphide) and black Graphite (elemental carbon) nodule inclusions. Small green hexagonal plates of natural Carborundum (CSi) have been found in the Canyon Diablo meteorites. The presence of the carbon suggests that there is a relationship between the IAB iron meteorites and Carbonaceous Chondrite meteorites. Similarity of trace element concentrations tends to confirm this conclusion.
Recent trace element concentration evaluations place the previous IIICD group in the IAB Main Group. IAB also is divided into several sub-groups according to the ratios of gold and nickel found. Thus the Toluca meteorites are now in sub-group sLL which is a low-gold, low-nickel sub-group. Another example is that the Australian Mundrabilla iron is paired with a similar meteorite, the Waterville iron from Washington state, as the "Mundrabilla duo" and is considered to be a IAB meteorite but not in the Main Group.