The crystal structures of hinsdalite, PbAl3[(P-0.69,S-0.31)O-4)](2)(OH,H2O)
(6), and of a plumbogummite containing a small amount of arsenic, PbAl3[(P-
0.95,As-0.05)O-4)](2)(OH,H2O)(6), have been refined in space group R (3) ov
er bar m, with a = 7.029(4) and c = 16.789(4) Angstrom, and a = 7.039(5) an
d c = 16.761(3) Angstrom, respectively. The refinements, using 258 (plumbog
ununite: 297) observed reflections with I greater than or equal to 3 sigma(
I), led to R = 3.0 % (3.7 %) and R-w = 3.0 % (3.2 %). Both minerals have th
e beudantite/crandallite structure type with hinsdalite being characterised
by disordered (P,S)O-4 tetrahedra with an average (P,S)-O distance of 1.52
Angstrom. The Pb atoms in both minerals are displaced from the origin and
are disordered about their sites, as in other Pb containing members of the
alunite family (beudantite, kintoreite, and plumbojarosite). The disorder o
f the Pb atoms is confined to the (0001) plane; in hinsdalite, Pb is at (0.
0312, 0.0312, 0.0), while in plumbogummite it is at (0.0409, 0.0409, 0.0).
Pb-O distances average 2.79 Angstrom in both minerals. The hydrogen-bonding
networks are modelled with the help of bond-valence summations.