New Data on Fiedlerite-1A from Ancient Slags of Lavrion, Greece: Crystal Structure and Hydrogen Bonding

Resumo

The crystal structure (R = 0.0750) of fiedlerite-1A Pb₃Cl₄F (OH) · H₂O from ancient slags of Lavrion (Greece) was studied on a single crystal. The mineral is triclinic, a = 8.5741 (7) Å, b = 8.0480 (5) Å, c = 7.2695 (4) Å, α = 90.087 (5), β = 102.126 (6), γ = 103.424 (6)°, V = 476.37 (6) ų, Z = 2. The Pb²⁺ cations center the Pb(1)F(H₂O)Cl₆, Pb(2)(OH)₂FCl₅, and Pb(3)(OH)F₂Cl₅ bicapped trigonal prisms. In the structure there is an additional position Pb', filled by 10% with Pb²⁺. There are two main structural fragments alternating along the a axis: (100) layers of Pb(2)- and Pb(3)-centred polyhedra and zigzag chains, stretched along the b axis formed by Pb(1)-centred polyhedra sharing common edges. The IR spectrum of fiederlite-1A is given.