Contribution to the crystal chemistry of Tl-sulfosalts. VI. Modular-level structure relationship between edenharterite TlPbAs3S6 and jentschite TlPbAs2SbS6

Edenharterite TlPbAs3S6 and jentschite TlPbAs2SbS6 are two members of the h utchinsonite family of merotypes. On modular level their crystal structures are composed of slabs which are (010)(SnS) cut-outs from the SnS-archetype with thickness alternating periodically between two and three coordination pyramids (N-1,N-2 = 2,3), The two structures are a special limiting case o f the above family because the regular 1 : 1 intergrowth of two different t ypes of slabs characteristic for this family has been reduced to a set of t ype layers only, Contrary to the description on polyhedral and chain levels the two structures cannot be regarded as homeotypes on the modular level. They have a substantial difference in the configuration of the boundary bet ween the slabs and in the orientation of adjacent slabs.