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Ghiaraite: A new mineral from Vesuvius volcano, Naples (Italy)

Manuela Rossi1, Fabrizio Nestola2,3, Federico Zorzi2, Arianna Lanza4, Luca Peruzzo3, Alessandro Guastoni5and Anatoly Kasatkin6

 
1Real Museo Mineralogico di Napoli, Università di Napoli, Via Mezzocannone 8, I-80134, Napoli, Italy
2Dipartimento di Geoscienze, Università di Padova, Via Gradenigo 6, I-35131, Padova, Italy
3CNR-IGG-Padova, Via Gradenigo 6, I-35131, Padova, Italy
4Departement für Chemie und Biochemie, Universität Bern, Freiestrasse 3, 3012, Bern, Switzerland
5Museo di Mineralogia, Università di Padova, Via Giotto 1, I-35122, Padova Italy
6V/O “Almazjuvelirexport”, Ostozhenka str. 22, block 1, 119034 Moscow, Russia
 
American Mineralogist, 99, 519-524, (2014)
 
Abstract
 
In this work we report the first finding of CaCl2β·4H2O, long known as a synthetic phase. The min­eral, called ghiaraite, was discovered in 2011 in a sample belonging to the Real Museo Mineralogico di Napoli (Italy), that had been collected in 1872 at Vesuvius volcano and stored in a glass sealed vial. It is associated with chlorocalcite (KCaCl3), hematite, sylvite, and halite. The mineral was found inside an ejecta of 5 m in size transported by a lava flow to the locality of Massa di Somma. Here with the ejecta still hot the sample was collected and rapidly stored in a sealed glass vial to preserve it from the atmospheric conditions. Ghiaraite is triclinic, space group P1, with unit-cell parameters: a = 6.3660(5), b = 6.5914(5), c = 8.5568(6) Å, α= 93.504(6)°, β= 97.778(7)°, γ= 110.557(6)°, V = 330.802(9) Å3, Z = 2. The calculated density is 1.838 g/cm3 using the ideal formula and the powder X‑ray diffraction data. It occurs as euhedral isometric grains up to 5–6 μm long intimately intermixed with chlorocalcite. The eight strongest reflections in the X‑ray powder diffraction pattern [listed as d(Å)(I)(hkl)] are: 2.628(100)(022); 2.717(88)(103); 4.600(88)(11 1); 2.939(77)(200); 2.204(75)(121), 5.874(73)(100), 6.124(47)(010); 3.569(46)(111). Ghiaraite was approved by the Commission on New Minerals, Nomenclature and Classification with IMA number 2012-072. The mineral was named in honor of Maria Rosaria Ghiara (b. 1948), Head of Real Museo Mineralogico of Napoli and Centro Musei delle Scienze Naturali e Fisiche dell’Università degli Studi di Napoli Federico II for her important work in promoting the scientific research focused on the mineralogy of Vesuvius volcano.
 
 
Key-words: Ghiaraite, new mineral, X‑ray diffraction, EDS, Vesuvius volcano, calcium tetrahy­drate chloride