THE CRYSTAL-STRUCTURE OF GANOMALITE, PB9CA5.44MN0.56SI9O33

A redetermination of the crystal structure of ganomalite, with composi tion Pb9Ca5.44(1)Mn-0.56(1)Si9O33, using new single crystal X-ray diff raction data is reported. Hexagonal space group symmetry P (6) over ba r, with Z = 1 and unit cell parameters a = 9.8456(3) Angstrom and c = 10.1438(4) Angstrom. The refinement of a structural model based on the Pb5Ge3O11 structure, with a partially occupied manganese position, re sulted in an R-value of 0.031. The arrangement of the SiO4 tetrahedra in ganomalite is an intermediate between the nasonite and pyromorphite structure, and the structure can be described as containing ''lead tu nnels'' based on Pb9O21 units extending through the structure.