X-Ray Studies on the Oxyhalide Minerals Nadorite (Ochrolite) PbSbO₂Cl and Ekdemite

Abstract

Recent investigations have revealed a family of very simply-built oxyhalides, containing bismuth together with another metal. These, compounds all form tetragonal plates; metal-oxygen sheets, which have in all substances the same construction, extend parallel to the largest faces. The ilíe-0-sheets are separated by halogen sheets, which may be single (^-compounds), double (X 2 ) or triple (X3). The tetragonal α-axis is always close to 3.9 Á, which is easily explained from the structure of the Me- Olayers (Sillén, 1940).We thought it of interest to search for the same simple construction principles in oxyhalides containing no bismuth. As first objects of study we chose the minerals nadorite, PbSb0 2 Cl, and ekdemite, a lead-arsenic oxychloride for which several different formulae have been proposed. The crystal structure of nadorite was worked out, and proved to be, in principle, an X 1 structure, where however the two sorts of metal atoms are ordered in rows, whereby the symmetry descends to orthorhombic. It could be shown that the mineral named ochrolite is identical with nadorite.Our work on ekdemite is also recorded. Here the conditions are more complex, and no certain conclusions could be drawn. Syntheses in the system PbSbOCl. TetragonalPbSb02Cl.Lead chloride was fused together with Sb 2 0 3 , mixtures of PbO and Sb 2 0 3 in various proportions, or PbO. Series of samples were prepared in porcelain crucibles and in evacuated tubes of Supremax glass; in both cases one series with rapid and one with slow cooling of the melts was made. The cooled product was ground and, for removal of the surplus of PbCl 2 , brought into a large beaker with cool water. After 5-10 hours of electric stirring the insoluble residue was filtered off and dried in a cool vacuum desiccator. The powder photographs revealed in these samples 1) a tetragonal phase, 2) nadorite, which is orthorhombic, 3) a phase which was obtained pure when PbO was added to PbCl 2 and which consequently contains no antimony. It seems improbable that the two first phases should contain antimony of higher valency than three, as they were obtained also

Lead-tellurium oxysalts from Otto Mountain near Baker, California: VI. Telluroperite, Pb3Te4+O4Cl2, the Te analog of perite and nadorite

“…Telluroperite possesses the Sillén X 1 structure-type (Sillén and Melander 1941) To consider the relationship between the stoichiometries of telluroperite, perite and nadorite, the formulas of all three minerals must be expressed in terms of two formula units per unit (Kraus and Nolze 1996). d calc based on the cell from the crystal-structure determination.…”

Mereheadite, Pb2O(OH)Cl: a new litharge-related oxychloride from Merehead Quarry, Cranmore, Somerset

“…The b angle is the stacking angle. As such, mereheadite is a member of the family of PbO-related layered lead-oxychlorides that includes nadorite, thorikosite and schwartzembergite, all of which are characterized by the alternation of PbO sheets with layers of chlorine atoms (Sillén and Melander, 1948;Giuseppetti and Tadini, 1973;Rouse and Dunn, 1985;Dunn and Rouse, 1985).…”

Crystal growth and X-ray investigation of a layered bismuth oxide sulfate in the CoSO4 —Bi2O3 system

“…The structure of [Bi t -^Co^O^ (SO^i-io.usxio.i8 is closely related to the nadorite type structure (Sillen and Melander 1941). This can easily be realised by applying to the monoclinic cell axes a, b, c, the following transformations: a' = a, b' = b, c' = a + 2c.…”