IVB meteorite

IVB meteorites
— Group —
Tlacotepec is one of 14 known IVB specimens; in contrast to most IVBs it is an octahedrite instead of an ataxite
Type	Iron
Structural classification	Most are ataxites (without structure) but show microscopic Widmanstätten patterns
Class	Magmatic
Subgroups	None?
Parent body	IVB
Composition	Meteoric iron (kamacite, taenite & tetrataenite); low in volatile elements, high in nickel & refractory elements
Total known specimens	14

IVB meteorites are a group of ataxite iron meteorites classified as achondrites. The IVB group has the most extreme chemical compositions of all iron meteorites, meaning that examples of the group are depleted in volatile elements and enriched in refractory elements compared to other iron meteorites.

The IVB meteorites are composed of meteoric iron (kamacite, taenite and tetrataenite). The chemical composition is low in volatile elements and high in nickel and refractory elements. Although most IVB meteorites are ataxites ("without structure"), they do show microscopic Widmanstätten patterns. The lamellae are smaller than 20 µm wide and lie in a matrix of plessite. The Tlacotepec meteorite is an octahedrite, making a notable exception, as most IVBs are ataxites.

Iron meteorites were originally divided into four groups designated by Roman numerals (I, II, III, IV). When more chemical data became available some groups were split. Group IV was split into IVA and IVB meteorites. The chemical classification is based on diagrams that plot nickel content against different trace elements (e.g. gallium, germanium and iridium). The different iron meteorite groups appear as data point clusters.