Meteorite identification involves several key tests to distinguish them from terrestrial rocks. First, the magnetic test is crucial, as most meteorites contain iron-nickel metal, making them magnetic. However, not all meteorites are strongly magnetic, so this test is not definitive. Next, the density test is performed, as meteorites are generally denser than Earth rocks due to their metal content. The streak test is another method, where a sample is rubbed on unglazed porcelain; meteorites typically leave no streak, unlike many Earth rocks.
The fusion crust examination is essential, as meteorites often have a thin, dark, glassy crust formed during atmospheric entry. Additionally, the interior examination can reveal a metallic, grainy texture with chondrules or metal flakes, which are indicative of meteorites. The regmaglypts or thumbprint-like impressions on the surface are also characteristic of meteorites.
Advanced tests include the chemical analysis using X-ray fluorescence (XRF) or inductively coupled plasma mass spectrometry (ICP-MS) to determine the elemental composition, which can confirm extraterrestrial origin. The isotopic analysis is another sophisticated test, often used to identify specific isotopic ratios unique to meteorites.
The petrographic microscope examination allows scientists to study thin sections of the sample under polarized light, revealing mineral structures and compositions typical of meteorites. Finally, the oxygen isotope analysis is a definitive test, as meteorites have distinct oxygen isotope ratios compared to Earth rocks.
These tests, often conducted in specialized laboratories, are essential for accurate meteorite identification. For more detailed methodologies, refer to resources from institutions like the University of Arizona's Lunar and Planetary Laboratory or the Meteoritical Society's publications.
