The Catalogue of Meteorites

Introduction to Meteorics

Stony-iron meteorites

The stony-irons are meteorite with approximately equal proportions of silicate minerals and iron-nickel metal. Stony-irons are sub-divided into two big groups, mesosiderites and pallasites, which have very different origins and histories.

A slice of the Esquel stony-iron (pallasite sub-division), found in Argentina in 1951 Pallasites: perhaps the most strikingly beautiful of all meteorites, pallasites are an approximately equal mixture of iron-nickel metal and silicates, predominantly olivine. They are presumed to represent material from the core-mantle boundary of their parent bodies. There are currently 50 known pallasites, almost all of which are Main Group (MG) pallasites. MG pallasites have oxygen isotope compositions similar to those of the HED achondrites. Typical example: Krasnojarsk.

Mesosiderites: the mesosiderites are a much more heterogeneous class of meteorites than the pallasites. They are a mixture of varying amounts of iron-nickel metal with a slice of the Estherville mesosideritedifferentiated silicates, the whole assemblage of which seems to have been brecciated. There are currently 66 known mesosiderites, sub-classified on the basis of textural and compositional differences within the silicate fraction of the meteorites. Like MG pallasites, mesosiderites have oxygen isotope compositions similar to those of the HED achondrites. Typical example: Estherville.