Dipartimento di Chimica - Univerità di Milano

The new mineral parascandolaite, isotypic to cubic perovskites, space group Pm3m (no. 221) is the natural analog of the synthetic fluoride KMgF3 and is related to neighborite, NaMgF3. It was found as a volcanic sublimate at Vesuvius volcano on 1944 eruption lava scoria, associated with opal, cerussite, mimetite, phoenicochroite and coulsellite. It occurs as transparent colorless to white cubic crystals up to 0.5 mm in length with vitreous luster. The density measured by flotation in a diiodomethane–toluene mixture is 3.11(1) g/cm3; that calculated from the empirical formula and single-crystal X-ray data is 3.123 g/cm3. The mineral is isotropic with n = 1.395(5) (580 nm). The six strongest reflections in the X-ray powder diffraction pattern are: [dobs in Å(I)(h k l)] 2.001(100)(2 0 0), 2.831(83) (1 1 0), 2.311(78)(1 1 1), 1.415(56)(2 2 0), 1.633(35) (2 1 1) and 1.206(22)(3 1 1). The unit-cell parameter is a = 4.0032(9) Å. The structure was refined to a final R(F) = 0.0149 for 35 independent observed reflections [I > 2σ(I)]. The mineral is named after the Italian mineralogist Antonio Parascandola (1902–1977).

The new mineral parascandolaite is the natural analog of the synthetic fluoride KMgF3. It was found as a volcanic sublimate at Vesuvius volcano on 1944 eruption.

As a part of the scientific agreement between the Dipartimento di Chimica - Università degli Studi di Milano and the Osservatorio Vesuviano (Napoli), the content of the bottles belonging to the historical collection of the Osservatorio, most of them collected before the 1944 eruption, was examined. The study allowed to identify several new phases, among which the recently described d’ansite-(Mn). In samples collected by A. Malladra in 1920, leonardsenite, MgAlF5(H2O)2, was identified. The mineral occurs as minute colorless prismatic crystals, wit maximum size of about 100 microns. The identification was obtained by single-crystal X-ray diffraction. The unit-cell data are: a 7.083(3); b 10.155(4); c 6.816(3) Å. This is the second discovery in the world.