TY - JOUR

T1 - Magnesiovesuvianite, Ca19Mg(Al,Mg)12Si18O69(OH)9, a new vesuvianite-group mineral

AU - Panikorovskii, Taras L.

AU - Shilovskikh, Vladimir V.

AU - Avdontseva, Evgenia Yu

AU - Zolotarev, Andrey A.

AU - Karpenko, Vladimir Yu

AU - Mazur, Anton S.

AU - Yakovenchuk, Victor N.

AU - Bazai, Ayya V.

AU - Krivovichev, Sergey V.

AU - Pekov, Igor V.

PY - 2017

Y1 - 2017

N2 - Magnesiovesuvianite (IMA 2015-104), ideally Ca19Mg(Al,Mg)12Si18O69(OH)9, a new vesuvianite-group member, was found in an old museum specimen labelled as vesuvianite from the Tuydo combe, near Lojane, Republic of Macedonia. It occurs as radiating aggregates up to 2 cm across consisting of acicular tetragonal crystals (up to 7 mm long and 5–40 μm thick) with distinct fibre-optic effect. Associated minerals are calcite, grossular–andradite and clinochlore. Single crystals of magnesiovesuvianite are transparent, light pink with a silky lustre. Dominant crystal forms are {100}, {110}, {101} and {001}. The Mohs’ hardness is 6. The measured and calculated densities are 3.30(3) and 3.35 g/cm3, respectively. Mineral is optically uniaxial, negative, ω = 1.725(2), ε = 1.721(2). The chemical composition (wt. % electron-microprobe data) is: SiO2 36.73, Al2O3 20.21, CaO 36.50, MgO 1.80, MnO 0.18, FeO 0.04, Na2O 0.01, H2O 3.10, total 98.37. The empirical formula based on 19 (Ca + Na) apfu is: (Ca18.99Na0.01)Σ 19.00(Mg0.60Al0.40)Σ 1.00(Al11.05Mg0.70Mn0.07Fe0.02)Σ 11.84Si17.84O68.72(OH)9. Absorption bands in the IR spectrum are: 393, 412, 443, 492, 576, 606, 713, 802, 906, 968, 1024, 3200, 3450, 3630 cm–1. The eight strongest lines of the powder X-ray diffraction pattern are (I–d(Å)–hkl): 23–10.96–110, 22–3.46–240, 33–3.038–510, 100–2.740–432, 21–2.583–522, 94–2.365–620, 19–2.192–710, 25–1.6165–672. Magnesiovesuvianite is tetragonal, space group P4/n, unit-cell parameters refined from the powder data are a 15.5026(3), c 11.7858(5), V 2832.4(2) Å3, Z = 2. The crystal structure has been refined to R1 = 0.027 for 3266 unique observed reflections with |Fo| ≥ 4σF. The structure refinements provided scattering factors of the Y1A,B sites close to 12 e– that supports predominant occupancy of these sites by the Mg2+ cations, in perfect agreement with the27Al MAS NMR data. Magnesiovesuvianite is a member of the vesuvianite group with Mg2+ as a dominant cation at the Y1 site. The name magnesiovesuvianite is given to highlight the species-defining role of Mg.

AB - Magnesiovesuvianite (IMA 2015-104), ideally Ca19Mg(Al,Mg)12Si18O69(OH)9, a new vesuvianite-group member, was found in an old museum specimen labelled as vesuvianite from the Tuydo combe, near Lojane, Republic of Macedonia. It occurs as radiating aggregates up to 2 cm across consisting of acicular tetragonal crystals (up to 7 mm long and 5–40 μm thick) with distinct fibre-optic effect. Associated minerals are calcite, grossular–andradite and clinochlore. Single crystals of magnesiovesuvianite are transparent, light pink with a silky lustre. Dominant crystal forms are {100}, {110}, {101} and {001}. The Mohs’ hardness is 6. The measured and calculated densities are 3.30(3) and 3.35 g/cm3, respectively. Mineral is optically uniaxial, negative, ω = 1.725(2), ε = 1.721(2). The chemical composition (wt. % electron-microprobe data) is: SiO2 36.73, Al2O3 20.21, CaO 36.50, MgO 1.80, MnO 0.18, FeO 0.04, Na2O 0.01, H2O 3.10, total 98.37. The empirical formula based on 19 (Ca + Na) apfu is: (Ca18.99Na0.01)Σ 19.00(Mg0.60Al0.40)Σ 1.00(Al11.05Mg0.70Mn0.07Fe0.02)Σ 11.84Si17.84O68.72(OH)9. Absorption bands in the IR spectrum are: 393, 412, 443, 492, 576, 606, 713, 802, 906, 968, 1024, 3200, 3450, 3630 cm–1. The eight strongest lines of the powder X-ray diffraction pattern are (I–d(Å)–hkl): 23–10.96–110, 22–3.46–240, 33–3.038–510, 100–2.740–432, 21–2.583–522, 94–2.365–620, 19–2.192–710, 25–1.6165–672. Magnesiovesuvianite is tetragonal, space group P4/n, unit-cell parameters refined from the powder data are a 15.5026(3), c 11.7858(5), V 2832.4(2) Å3, Z = 2. The crystal structure has been refined to R1 = 0.027 for 3266 unique observed reflections with |Fo| ≥ 4σF. The structure refinements provided scattering factors of the Y1A,B sites close to 12 e– that supports predominant occupancy of these sites by the Mg2+ cations, in perfect agreement with the27Al MAS NMR data. Magnesiovesuvianite is a member of the vesuvianite group with Mg2+ as a dominant cation at the Y1 site. The name magnesiovesuvianite is given to highlight the species-defining role of Mg.

KW - Cation ordering

KW - Light conductor

KW - Lojane

KW - Magnesiovesuvianite

KW - New mineral

KW - Republic of macedonia

UR - http://www.scopus.com/inward/record.url?scp=85018297284&partnerID=8YFLogxK

U2 - 10.3190/jgeosci.229

DO - 10.3190/jgeosci.229

M3 - Article

AN - SCOPUS:85018297284

VL - 62

SP - 25

EP - 36

JO - Journal of Geosciences

JF - Journal of Geosciences

SN - 1802-6222

IS - 1

ER -