INVESTIGATING IRON METEORITES: MINERALOGY AND MICROSTRUCTURAL ANALYSIS

Meteorites, extraterrestrial materials that impact Earth, are traditionally categorized into chondrites, achondrites, stony-iron, or iron meteorites. Among these, iron meteorites are highly remarkable due to their Fe-Ni alloy composition, accompanied by small quantities of sulphides and carbides. Despite their significance, iron meteorites are exceptionally rare, comprising approximately 5% of all known meteorites. Their study is of great interest as they are believed to have formed as the cores of asteroids, providing valuable insights into the composition of the metallic cores of terrestrial planets such as Mercury, Venus, Mars, and Earth. In this undergraduate project, we examine three iron meteorite samples generously provided by the School of Physical Sciences of the University of Arkansas at Little Rock. The specimens underwent preparation procedures, including diamond coating thin blade cutting with low-speed cutting fluid, followed by mirror polishing using colloidal alumina suspension (0.03 μm grit). To expose only the polished surface, the samples were coated with steel lacquer and subsequently acid etched with varying concentrations of nitric wash (5%, 10%, and 15%) for 2 to 4 minutes. As a result of these treatments, the samples revealed a distinct Widmanstätten pattern, attributed to relatively high Ni (wt%) content with fine crystals of potential kamacite hosted within a taenite matrix.

Presently, ongoing research focuses on utilizing Electron Dispersive Spectrometry (EDS) to investigate the chemical composition of the first observed phases and other phases present at smaller scale. Additionally, the meteorite textures will be subjected to higher resolution analysis using a Scanning Electron Microscope (SEM) to gain a more detailed understanding. Furthermore, future work will employ high-resolution microprobe analyses in combination with highly polished samples using vibrational polishing with colloidal silica, aiming to achieve accurate quantitative measurements for precise classification of each meteorite, and to determine the presence and characteristic of potential nano minerals.