A note on Metallographic Techniques for Iron Meteorites
Meteorites are particularly fascinating subjects for metallographic examination, not merely because of their extraterrestrial origin, but also because of the rich variety of microstructural constituents encountered. While their structure can be assessed use of the familiar nital and picral etchants used extensively for steels, application of selective etchants, including those that produce selective coloration, greatly increases the amount of information
obtained by light microscopy. The article describes efforts to preferentially darken or color microstructural constituents in iron meteorites: kamacite (ferrite), Neumann bands (mechanical twins), taenite (austenite), cohenite (Fe-Ni carbide similar to cementite), martensite and schreibersite/rhabdite (Fe-Ni phosphides). The influence of concentration gradients, deformation, and reheating on the structure can be clearly observed by the use of tint etchants.