IVA Iron Meteorites
Description: The members of the IVA group of iron meteorites are mostly fine octahedrites, and they display a unique trace element pattern of extraordinarily low germanium and low gallium values. Some IVA iron meteorites contain sparsely distributed small nodules of troilite and graphite, although silicate inclusions are rare to absent in most members (with the exception of the highly silicated meteorite of Steinbach that is discussed below).
Formation history & Origin: More recent research suggests that the IVA iron meteorites formed in the core of a small, differentiated asteroid that was disrupted by a major impact shortly after its formation. After the asteroid was reaccreted, it was again disrupted about 450 million years ago.
Members: There are about 65 members in this well-represented group of irons. The famous meteorite Gibeon is a rather typical member of this group, and more than 30 tons of this IVA iron meteorite have been recovered from its large, prehistoric strewn field in Namibia. However, one anomalous, silicate-rich IVA member, Steinbach, is of major scientific interest. This historic German find consists of nearly equal parts of a IVA nickel-iron matrix and reddish silicates; these silicates are a mixture of pyroxenes and the rare mineral tridymite. It is still heavily debated whether this beautiful silicated iron represents a IVA analog to the pallasites, those true stony-iron meteorites that formed at the core/mantle boundary of their parent body, or if Steinbach is just a secondary product, formed during the reaccretion of the IVA parent body following the first disrupting impact.