Published online by Cambridge University Press: 05 July 2018
The Angra dos Reis (iron) has been studied metallographically and an attempt has been made to discuss the circumstances under which the following elements of structure formed: clear etching and frosty etching kamacite, decorated Neumann lines, giant rhabdites, plate rbabdites, rhabdite clusters, microrhabdites, cohenite, and remelted troilite. The remelted troilite is taken to indicate a shock event. However, since there are no metallographically visible indications of shock in the kamacite and since the back reflection X-ray diffraction pattern shows only very faint Debye-Scherrer arcs superimposed on a pattern of sharp spots, it is concluded that the shock event took place at a temperature that allowed shock effects to anneal out of the kamacite almost completely. A submicroscopic precipitate in the metallic matrix is observable with the electron microscope and may represent the final precipitation of phosphide from shocked kamacite.