Crystal structure of synthetic Pb (sub 12.65) Sb (sub 11.35) S (sub 28.35) Cl (sub 2.65) ; a new view of the crystal chemistry of chlorine-bearing lead-antimony sulphosalts

The structure of this new synthetic sulphosalt prepared at 420 degrees C has been determined by X-ray structure analysis using site-occupancy refinement and bond-valence methods. EPMA gave Pb 52.7, Sb 28.2, S 18.1, Cl 1.9, =100.9. It is monoclinic, with a 19.512, b 4.052, c 35.134 Aa, beta 96.34 degrees , V 2761 Aa (super 3) ; space group I2/m, Z = 2; D (sub calc.) 6.032 g/cm (super 3) . The crystal structure is closely related to that of dadsonite; the special position 1/2,1/2,0 is entirely occupied by Cl. Other Cl atoms partially substitute on specific S positions, in connection with mixed Pb,Sb sites; the major Cl content is due to this second substitution rule, and may play a fundamental role in the crystal chemistry of Cl-rich Pb-Sb sulphosalts.