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Mineralogical ClassificationIMA 2017-113 = jahnsite–(MnMnZn)
26th Feb 2019 13:23 UTCMarco E. Ciriotti Manager
▪ Kampf, A.R., Alves, P., Kasatkin, A., Škoda, R. (2019): Jahnsite–(MnMnZn), a new jahnsite-group mineral, and formal approval of the jahnsite group. European Journal of Mineralogy, 31, 167-172.
Abstract:
Jahnsite–(MnMnZn) (IMA2017-113), Mn2+2Zn2Fe3+2(PO4)4(OH)2·8H2O, is a new member of the jahnsite group from the Herdade dos Pendões mine, Beja district, southwest Portugal. It formed in a highly altered gossan in association with Zn-bearing libethenite, quartz, rhodochrosite and santabarbaraite. It occurs in sub-parallel bundles of light golden brown prisms up to 0.3 mm long. Crystals are transparent with vitreous to silky lustre and white streak. The mineral is brittle with irregular, splintery fracture, good cleavage parallel to {001} and Mohs’ hardness of about 4. The measured density is 2.89(2) g cm-3. Optically, it is biaxial (+), with α = 1.655(2), β = 1.662(2), γ = 1.673(2) (white light); 2V = 78(1)°; pleochroism: X nearly colourless, Y and Z beige; X < Y ≈ Z. Electron microprobe analyses gave the empirical formula (Mn2+0:71Na0.15Ca0.10)Σ0:96(2+1.00)(Zn1.00Mn2+0.66Fe2+0.21Mg0.10Fe3+0.03)Σ2.00(Fe3+1.99Al0.01)Σ2:00(P1.01O4)4(OH)2 · 8H2O. Jahnsite–(MnMnZn) is monoclinic, P2/a, a = 15.222(6), b = 7.187(6), c = 10.028(5) Å, β = 111.746(16), V = 1019.0(11) Å3 and Z = 2. The eight strongest lines in the X-ray powder diffraction pattern are [dobs/Å (I) (hkl)]: 9.25 (63) (001), 5.00 (40) (210,21-1,111), 4.648 (33) (002), 3.509 (41) (40-2), 2.842 (100) (022), 1.9984 (37) (422,42-4), 1.9506 (30) (024) and 1.5853 (33) (820,82-4). The jahnsite group has now been officially established by the Commission on New Minerals, Nomenclature and Classification. The general formula for jahnsite-group minerals is XM1M22M32(H2O)8 (OH)2(PO4)4; the ionic radii for the cation sites generally increase as follows: M3 < M2 < M1 < X, and the M3 site determines whether the species belongs to the jahnsite subgroup (M3 = Fe3+) or the whiteite subgroup (M3 = Al). The subgroup name is generally used as the species root name to be followed by a suffix of the form –(XM1M2). Using this as a guide for the jahnsite described herein results in the following site assignments: X = Mn, M1 = Mn, M2 = Zn, and M3 = Fe; and the name jahnsite–(MnMnZn).
26th Feb 2019 16:00 UTCLuís Martins 🌟
27th Feb 2019 15:00 UTCMarco E. Ciriotti Manager
Ciao.
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Copyright © mindat.org and the Hudson Institute of Mineralogy 1993-2024, except where stated. Most political location boundaries are © OpenStreetMap contributors. Mindat.org relies on the contributions of thousands of members and supporters. Founded in 2000 by Jolyon Ralph.
Privacy Policy - Terms & Conditions - Contact Us / DMCA issues - Report a bug/vulnerability Current server date and time: May 7, 2024 07:16:04