Epitaxies of Ca sulfates on calcite (CaCO3). III. {010}, {001}, {100} and {011} growth forms of anhydrite (CaSO4) deposited on the {10.4} rhombohedron of calcite

Anhydrite (CaSO 4 ) and calcite (CaCO 3 ) are two of the main mineral structures on which there is no longer any discussion today. The problem is different when it comes to analyzing the crystal chemical relationships between them and, in particular, the crystallography arising at the epitaxial interfaces between Ca sulfates (deposits) and the peculiar {10.4} form of cleaved calcite (substrate). Recently, Ca sulfates replacing calcite have acquired great importance in addressing the epitaxy challenge. The crystallographic epi-interactions between CaSO 4 ·2H 2 O gypsum and CaSO 4 ·0.5H 2 O bassanite and the {10.4} form of calcite have already been analyzed in detail by this research group [Aquilano et al. (2022). CrystEngComm , 24 , 5120–5127; Aquilano et al. (2022). J. Appl. Cryst. 55 , 1289–1296] (parts I and II, respectively). This work is intended to complete the research, presenting the re-evaluation (part III) of anhydrite (CaSO 4 ) epitaxially matching on the {10.4} rhombohedron of calcite.