The Lafayette meteorite has an unknown provenance. It was “rediscovered” in 1931 in Purdue University, Lafayette, Indiana, USA. Lafayette is a single oriented 800 gram stone with a fusion crust showing well-developed flow features. Isotopic techniques have produced ages of 1.33 Ga (Ar-Ar) and 1.32 Ga (Sm-Nd). Lafayette landed on Earth 3,000-4,000 years ago.
The mineral assemblage is dominated by clinopyroxene (augite) with olivine, orthopyroxene and plagioclase feldspar occurring in lower abundances. Minor species include K-feldspar, chlorapatite, titaniferous magnetite and the sulphides chalcopyrite and marcasite.
Compositionally, Lafayette is similar to the Nakhla and Governador Valadares meteorites, but contains more extra-terrestrial water and alteration material than either of them. This alteration assemblage consists of smectite, serpentine, gypsum and a siderite-phyllosilicate-Fe oxide-hydrated silicate gel.