A post-stishovite phase of silica was identified in the Shergotty meteorite
by x-ray diffraction and field emission scanning electron microscopy. The
diffraction pattern revealed a monoclinic Lattice, similar to the baddeleyi
te-structured polymorph with the cell parameters a = 4.375(1) angstroms, b
= 4.584(1) angstroms, c = 4.708(1) angstroms, beta = 99.97(3), rho = 4.30(2
) grams per cubic centimeter, where the numbers in parentheses are the maxi
mum deviations. Transmission electron microscopy investigations indicate th
e presence of the alpha-lead dioxide-like polymorph, stishovite, and second
ary cristobalite in the same silica grain. The mixture of high-density poly
morphs suggests that several post-stishovite phases were formed during the
shock event on the Shergotty parent body.