Characterisation of contact twinning for cerussite, PbCO3, by single-crystal NMR spectroscopy

Cerussite, PbCO 3 , like all members of the aragonite group, shows a tendency to form twins, due to high pseudo-symmetry within the crystal structure. We here demonstrate that the twin law of a cerussite contact twin may be established using only 207 Pb-NMR spectroscopy. This is achieved by a global fit of several sets of orientation-dependent spectra acquired from the twin specimen, allowing to determine the relative orientation of the twin domains. Also, the full 207 Pb chemical shift tensor in cerussite at room temperature is determined from these data, with the eigenvalues being δ 11 = ( - 2315 ± 1 ) ppm, δ 22 = ( - 2492 ± 3 ) ppm, and δ 33 = ( - 3071 ± 3 ) ppm.