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- Title
Alumovesuvianite, CaAl(Al,Mg)SiO(OH), a new vesuvianite-group member from the Jeffrey mine, asbestos, Estrie region, Québec, Canada.
- Authors
Panikorovskii, Taras; Chukanov, Nikita; Aksenov, Sergey; Mazur, Anton; Avdontseva, Evgenia; Shilovskikh, Vladimir; Krivovichev, Sergey
- Abstract
Alumovesuvianite (IMA 2016-014), ideally CaAl(Al,Mg)SiO(OH), is a new vesuvianite-group member found in the rodingite zone at the contact of a gabbroid rock with host serpentinite in the abandoned Jeffrey mine, Asbestos, Estrie Region, Québec, Canada. It occurs as prismatic tetragonal crystals up to 4 × 4 × 6 mm in size encrusting walls of cavities in a granular diopside. Associated minerals are diopside, grossular and prehnite. Single crystals of alumovesuvianite are transparent colorless or light pink with a vitreous lustre. The dominant crystal forms are {100}, {110}, {210}, {111}, {101} and {001}. The Mohs hardness is 6.5. The specific gravitiy is D = 3.31(1) g/cm and D = 3.36 g/cm, respectively. The mineral is optically uniaxial (−), ω = 1.725(2), ε = 1.722(2). The chemical composition, determined by SEM-WDS (wavelength-dispersive spectroscopy on a scanning electron microscope; all oxides except HO) and TG (thermogravimety; HO) analysis, is: SiO 37.1 wt%, AlO 18.8 wt%, CaO 36.6 wt%, MgO 2.48 wt%, MnO 0.67 wt%, FeO 0.22 wt%, HO 2.61 wt%, total 98.5 wt%. The empirical formula based on 19 Ca atoms per formula unit and taking into account the MAS-NMR (magic-angle spinning nuclear magnetic resonance) data, is: Ca(AlFe )(AlMgMn )SiO(OH). The most intense IR absorption bands lie in the ranges 412-609, 897-1024, and 3051-3671 cm. The eight strongest lines of the powder X-ray diffraction pattern are ( I-d(Å)- hkl): 22-2.96-004, 100-2.761-432, 61-2.612-224, 25-2.593-600, 20-1.7658-831, 20-1.6672-734, 21-1.6247-912, and 22-1.3443-880. Alumovesuvianite is tetragonal, space group P4/ n, unit-cell parameters refined from the powder data are a = 15.5603(5) Å, c = 11.8467(4) Å, V = 2868.3(4) Å, Z = 2. The crystal structure has been refined to R = 0.036 for 3098 unique observed reflections with | F | ≥ 4σ. The structure refinement provides the < Y1A-O > bond length of 1.916 Å and the scattering factor for the Y1 site of 16 e , which is in good agreement with the total occupancy of this site as (AlMn Fe ) and is confirmed by the Al MAS NMR data. Alumovesuvianite is a new member of the vesuvianite group with Al as a dominant cation in the Y1 site. The name alumovesuvianite is given to highlight the species-defining role of Al.
- Subjects
VESUVIANITE; ASBESTOS; PREHNITE; SCANNING electron microscopy; WAVELENGTH dispersive X-ray spectroscopy
- Publication
Mineralogy & Petrology, 2017, Vol 111, Issue 6, p833
- ISSN
0930-0708
- Publication type
Article
- DOI
10.1007/s00710-017-0495-1