Crystals of the rare lead mineral barstowite, Pb4Cl6(CO3).H2O, were found on a lead object from a Late-Hellenistic shipwreck and within Etruscan iron slags. Its crystal structure was determined and refined to R = 0.023. Barstowite crystallizes in the monoclinic space group P21/m with a 4.2043(8) Å, b 9.199(2) Å, c 16.663(3) Å, beta 91.82(1). The lead atoms are nine-fold coordinated in form of tricapped trigonal prisms by chlorine and oxygen atoms. The polyhedra, through sharing of faces, edges and corners, define structural layers which are linked together in a three-dimensional framework. Oxygen atoms belonging to the water molecules form hydrogen bonds with oxygens of the carbonate groups. The relationship of barstowite with cotunnite and phosgenite is shortly discussed.
The crystal structure of barstowite, Pb4Cl6(CO3)·H2O, determined on crystals from Etruscan slags and from a Late-Hellenistic shipwreck
MERLINO, STEFANO;PASERO, MARCO;PERCHIAZZI, NATALE;
2000-01-01
Abstract
Crystals of the rare lead mineral barstowite, Pb4Cl6(CO3).H2O, were found on a lead object from a Late-Hellenistic shipwreck and within Etruscan iron slags. Its crystal structure was determined and refined to R = 0.023. Barstowite crystallizes in the monoclinic space group P21/m with a 4.2043(8) Å, b 9.199(2) Å, c 16.663(3) Å, beta 91.82(1). The lead atoms are nine-fold coordinated in form of tricapped trigonal prisms by chlorine and oxygen atoms. The polyhedra, through sharing of faces, edges and corners, define structural layers which are linked together in a three-dimensional framework. Oxygen atoms belonging to the water molecules form hydrogen bonds with oxygens of the carbonate groups. The relationship of barstowite with cotunnite and phosgenite is shortly discussed.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
