Asterix, an iron-rich world in the Sadalmelik system
Worlds composed of more than 80% core, usually iron and other siderophilic elements.
These worlds form either in very close solar orbits or about very hot and active suns. In either case, much of the lighter planet-building material has been blown away by the intense young solar winds or separated by other active processes in the protoplanetary cloud. This leaves only the heavier elements behind to form planets. Such worlds tend to be small, although they may attain very large sizes in high metal content systems.
Smaller ferriniian worlds are typically heavily cratered, often with signs of primordial geologic activity. The only atmosphere that they are likely to have is a trace layer of helium being constantly replenished and stripped away by the sun's stellar wind. Example Asterix.