We have developed a procedure for the analysis of possible epitaxial contacts of crystalline phases, which was based on the close-packed atomic planes in the structures. The geometric similarity of the atomic nets in the structures of natural mercury-containing sulfides and oxohalides to elucidate the formation of their natural associations was exemplified. The procedure may be used to analyze the contacts of the crystal structures of any compounds. (C) 2010 Elsevier B.V. All rights reserved.