The intracrystalline cation distributions in fourteen natural Zn-aluminate spinels were determined by means of X-ray single-crystal structural refinement, supported for some samples by Mossbauer spectroscopy. Zinc substitutes for Mg and subordinately Fe (super 2+) and its relevant changes in content, from 0.10 to 0.96 atoms per formula unit (apfu), are not related to variations of cell parameter. The latter is determined mainly by the substitution Fe (super 3+) <-->Al. In agreement with data from synthetic samples, a small but definite amount of Zn (up to 0.06 apfu) is located in the octahedral M site. Fe (super 2+) , when present, shows a preference for tetrahedral coordination. An improved value of the tetrahedral Zn(T)-O distance (1.960 Aa) was obtained, integrating the set of interatomic distances used for the determination of cation distribution in spinels.
Other|February 01, 1998
Cation distribution in natural Zn-aluminate spinels
Mineralogical Magazine (1998) 62 (1): 41-54.