Small, hemimorphic hexagonal crystals implanted on botryoidal zinc sulfide from the Zig Zag Mine, Joplin, Missouri, have been studied by crystallographic and x-ray diffraction techniques. They are identified as a new wurtzite polytype, wurtzite-10H. The unit cell data are: space group, P63mc; a = 3.824 Å, c = 31.20 Å; cell contents, 10ZnS. Comparison of diffraction intensity data indicates that the published structure of SiC-10H (stacking sequence 3223) is different from that of wurtzite-10H. Calculation of intensities for various models shows that the stacking sequence for wurtzite-10H is 55. Crystals of wurtzite from Joplin described by A. F. Rogers (1904) were evidently wurtzite-10H. Powder diffraction data revealed the presence of another polytype, wurtzite-8H, with a hexagonal unit cell: space group P63mc; a = 3.82 Å, c = 24.96 Å; cell contents 8ZnS. Wurtzite-6H was also found at the Zig Zag Mine. The wurtzite polytypes evidently form a homologous series (2H, 4H, 6H, 8H, 10H) resulting from growth phenomena based on screw dislocations.

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