Background
While it can be very difficult to confirm that something is a meteorite, the presence of several minerals along with other physical characteristics often provides evidence. Coesite and stishovite (SiO2) are the two key indicator silicon oxides found in meteorites and asteroids. They are formed under high pressure and high temperature conditions that meteorites or asteroids experience during an impact event. Their crystal structures are different from that of alpha-quartz (SiO2), which is a mineral naturally and widely found in the Earth's continental crust, although their chemical formulas are the same. X-ray diffraction is an ideal analysis technique to distinguish those materials and identify the indicators such as coesite and stishovite.
Investigation
A piece of possible meteorite was studied on Rigaku's MiniFlex benchtop diffractometer. The diffraction pattern obtained was carefully compared with the database of known materials for phase identification. The results of the comparison analysis are shown in Figure 1.
Figures 2 through 4 show the crystal structures of alpha quartz and the meteorite indicators, coesite and stishovite. The simultaneous presence of coesite and stishovite along with alpha quartz and hematite in the powder pattern strongly suggests the meteoritic nature of this piece. The results show that X-ray diffraction can identify those key materials.
