The crystal structure of Pb₅(As³⁺O₃)Cl₇from the historic slags of Lavrion, Greece – a novel Pb(II) chloride arsenite

Abstract

The crystal structure of new lead chloride arsenite, Pb5(As3+O3)Cl7 [orthorhombic, Pbcn, a = 16.894(2), b = 10.913 (1), c = 16.760(2) Å, V = 3090.1(7) Å3], from the historic slags of Lavrion, Greece, has been solved by direct methods and refined to R1 = 0.069. The structure contains five symmetrically unique Pb, one As, eight Cl and three O sites. The As atom forms three nearly equal As—O bonds which result in the formation of an AsO3 trigonal pyramid with As at the apex. The Pbl. Pb2, Pb3 and Pb4 atoms are bonded to the AsO3 groups via Pb2+—O bonds to form complex [Pb4(AsO3)] chains parallel to the b axis. The Pb(5) atom is coordinated solely by Cl– anions. The resulting Pb(5)Cl7 polyhedra share common edges and corners to produce bent chains parallel to the c axis. A short compilation of structural features of known lead chloride arsenites is given.

Pb2(AsO2OH)Cl2, a new phase from the Lavrion ancient slags, Greece: occurrence and characterization

“…It is a rolled fragment of black metallurgical slag with gas cavities (Fig. 1) containing colourless transparent prismatic crystals of Pb 2 (AsO 2 OH)Cl 2 , up to 0.7 mm in length, associated with phosgenite and isometric colourless crystals of a phase with a composition Pb 5 (AsO 3 )Cl 7 , which was described in our previous work (Siidra et al, 2011). These lead arsenites are both reported from the natural environment for the first time, but their occurrence in anthropogenic slag means that in accordance with the modern rules of the IMA Commission on New Minerals, Nomenclature and Classification (Nickel, 1995) they cannot be considered to be valid mineral species.…”

“…The Pb(2) atoms form two short bonds to O(2) and five longer (>2.9 Å ) bonds to OH(1) and Cl atoms (Table 3) is due to the stereoactivity of lone electron pairs on the Pb 2+ cations, and is in good agreement with general observations for structures containing cations with stereoactive electron pairs (Brown, 1974). It is noteworthy that in the recently described compound Pb 5 (AsO 3 )Cl 7 (Siidra et al, 2011), Pb coordination is more symmetrical with a nearly equal distribution of bond lengths around the central atom. This observation is in good agreement with the suggestion (Siidra et al, 2008a) that the stereochemical activity of the lone electron pair on Pb 2+ cations is more pronounced when the structure contains strong Lewis bases (Jensen, 1980).…”

The Lavrion Mines: A Unique Site of Geological and Mineralogical Heritage

“…Twenty-three minerals were first reported from Lavrion mines (e.g., attikaite, glaucocerinite, ktenasite, kapellasite, hilarionite, zinkolivenite, agardite-(Nd), nickeltsumcorite, kamarizaite and serpierite and several Cd-Zn-bearing sulfates as niedermayrite, lazaridisite, voudourisite, drobecite, and katerinopoulosite from the Esperanza mine [82,87,88,91,95]) (Table 1). Others were first discovered in antique Lavrion slags where they formed by interaction with seawater (e.g., fiedlerite, thorikosite, georgiadesite, nealite, paralaurionite, and penfieldite) [102][103][104][105][106][107][108][109][110]. These so-called slag minerals are formed in sites where metallurgical wastes occur and represent the products of recent re-distribution of metals and subsequent precipitation in the form of oxides, hydroxides, or salts.…”

The crystal structure of the compound Pb6Cu+(AsO3)2Cl7 discovered in the ancient slags of Lavrion, Greece

“…Different topologies of arsenite groups (i.e., isolated groups, As 2 O 5 diarsenite groups, vierer single chains and open-branched zweier chains) in lead chloride arsenites are described by Siidra et al [5]. In the crystal structure of Pb 6 Cu(AsO 3 ) 2 Cl 7 from Lavrion, arsenite groups are isolated from each other.…”