• journal_title：Mineralogical Magazine
• Contributor：O. I. Siidra ; N. V. Chukanov ; I. V. Pekov ; S. V. Krivovichev ; A. Magganas ; A. Katerinopoulos ; P. Voudouris
• Publisher：Mineralogical Society of Great Britain and Ireland
• Date：2012-
• Format：text/html
• Language：en
• Identifier：10.1180/minmag.2012.076.3.10
• journal_abbrev：Mineralogical Magazine
• issn：0026-461X
• volume：76
• issue：3
• firstpage：597
• section：Articles

Transparent prismatic crystals of Pb₂(AsO₂OH)Cl₂ were collected in black metallurgical slag on the coast in the Punta Zeza area, 3 km south of the town of Lavrion, Greece. Analyses by energy-dispersive X-ray spectrometry (EDS) provided the following chemical composition: PbO 73.04, As₂O₃ 15.97, Cl 11.42, O=Cl −2.58, total 97.85 wt.%. The empirical formula calculated on the basis of As = 1 is H_xPb_2.03(AsO₃)_1.00Cl_1.995 (x = 0.96). The infrared spectrum of Pb₂(AsO₂OH)Cl₂ has characteristic bands at 707 and 594 cm⁻¹, O–H stretching vibrations at 3310 and 2900 cm⁻¹ and a band at 1107 cm⁻¹ which is assigned to As–O–H bending vibrations. The structure, which is monoclinic P2₁/m, a = 6.4235(8), b = 5.5399(7), c = 9.321(1) Å, β = 90.767(2)°, V = 331.67(7) ų, R₁ = 0.035, is identical to that of synthetic Pb₂(AsO₂OH)Cl₂ and contains two symmetrically unique Pb sites and one As site. The crystal structure is based on [Pb₂AsO₂OH]²⁺ double chains interconnected via weak Pb–Cl bonds to produce a three-dimensional framework which is closely related to that of Pb oxysalt minerals containing [O₂Pb₃]²⁺ chains of oxocentred [OPb₄]⁶⁺ tetrahedra including mendipite, damaraite, rickturnerite and plumboselite.