First crystal-structure determination of chromites from an acapulcoite and ordinary chondrites

We report the first crystal structure determinations of chromites from an acapulcoite and from ordinary chondrites. Cell edges range from 8.3212 (3) to 8.3501 (1) Å, while the oxygen positional parameters are in the range 0.2624 (3) to 0.26298 (9). Their compositions show they are very close to the chromite end-member FeCr2O4 with limited Al and Mg content. Titanium oxide content exceeds 1%, whereas the amount of Fe3+ is negligible. Extraterrestrial chromite is readily distinguished from terrestrial analogues on the basis of cell edge and oxygen positional parameter. These distinctions will facilitate ongoing attempts to reconstruct the paleoflux of meteorites to Earth from resistant extraterrestrial spinel grains recovered from ancient sediments.