The fumarolic mineralogy of the Icelandic active volcanoes, the Tyrrhenian volcanic belt (Italy) and the Aegean active arc (Greece) is investigated, and literature data surveyed in order to define the characteristics of the European fumarolic systems. They show broad diversity of mineral associations, with Vesuvius and Vulcano being also among the world localities richest in mineral species. Volcanic systems, which show recession over a longer period, show fumarolic development from the high-temperature alkaline halide/sulphate, calcic sulphate or sulphidic parageneses, synchronous with or immediately following the eruptions, through medium-temperature ammonium minerals, metal chlorides, or fluoride associations to the late low-temperature paragenesis dominated by sulphur, gypsum, alunogen, and other hydrous sulphates. The situation can be different in the systems that are not recessing but show fluctuations in activity, illustrated by the example of Vulcano where the high-temperature association appears intermittently. A full survey of the mineral groups and species is given in respect to their importance and appearance in fumarolic associations

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The hydrocerussite-related phase, NaPb5(CO3)4(OH)3, has been found as colourless lamellar crystals in cavities within a pebble of the ancient marine slag collected in the Pacha Limani area of the Lavrion mining district, Attiki, Greece. This phase of anthropogenic origin was characterized by electron microprobe, infrared spectroscopy, powder and single-crystal X-ray diffraction. The unique crystal structure (P63/mmc, a = 5.2533(11), c = 29.425(6) Å, V = 703.3(3) Å3 and R1 = 0.047) is based upon structurally and chemically different electroneutral blocks. Each of the blocks can be split into separate sheets. The outer sheets in each block are topologically identical and have the composition [PbCO3]0. The [Pb(OH)2]0 lead hydroxide sheet is sandwiched between the two [PbCO3]0 sheets resulting in the formation of the first block [Pb3(OH)2(CO3)2]0 structurally and compositionally identical to that one in hydrocerussite Pb3(OH)2(CO3)2. Similarly the [Na(OH)]0 sheet is sandwiched between another two [PbCO3]0 sheets thus forming the [NaPb2(OH)(CO3)2]0 block described previously in the structure of abellaite NaPb2(OH)(CO3)2. Stereochemically active lone electron pairs on Pb2+ cations are located between the blocks. There are two blocks of each type per unit cell, which corresponds to the following formula: [Pb3(OH)2(CO3)2][NaPb2(OH)(CO3)2] or NaPb5(CO3)4(OH)3 in the simplified representation. The formation of NaPb5(CO3)4(OH)3 in Lavrion slags is by the contact of lead-rich slags with the sea water over the last two thousand years.

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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.