..., Genova, Liguria, Italy. It occurs as orange-reddish prismatic crystals, up to 200 μm in length, with a vitreous lustre, associated with braunite, quartz, calcite, As-rich medaite, calcian rhodocrosite, talc, and ganophyllite. Electron microprobe analysis of arsenmedaite gave (in wt%): V 2 O 5 = 1.84...

...+ ,V 5+ )O 22 ](OH) 6 , Z = 2, tiragalloite - \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(\mathrm{Mn}_{4}^{2+}\) \end{document} [Si 3 As 5+ O 12 (OH)], Z = 4 and medaite - \batchmode...

...Carlo Maria Gramaccioli; William L. Griffin; Annibale Mottana Abstract Medaite occurs as small brown grains, intimately associate with tiragalloite, in veinlets cutting black, massive aggregates of braunite and quartz from an abandoned manganese mine at Molinello, near Chiavari, Liguria, Italy...

...F ig . 3. Petrography of sediment-hosted stratiform Fe–Mn ores in Val Ferrera. (a) Outcrop of hematite–quartz ore at Fianel, showing lenticular bedding. (b) Outcrop of medaite-rich (orange vanadatosilicate) mixed Fe–Mn silicate–oxide ore at Fianel. (c) Mn ore (dark: mainly rhodonite...

... is 5.7204 and P is [2 F c 2  + Max( F o 2 ,0)]/3. Medaite was also found in alpeite-free veins crosscutting the Mn ore at Monte Alpe ( Castellaro & Passarino, 2011 ). The absence of alpeite in those veins seems to suggest that the formation of a vanadium-bearing ardennite phase...

.... C. Biagioni, D. Belmonte, C. Carbone, R. Cabella, F. Zaccarini, and C. Balestra (2019) Arsenmedaite, Mn 6 2 + As 5+ Si 5 O 18 (OH), the arsenic analogue of medaite, from the Molinello mine, Liguria, Italy: occurrence and crystal structure. European Journal of Mineralogy, 31(1), 117...

... mines ( Cortesogno & Galli, 1974 ; Cortesogno et al. , 1979 ; Cabella et al. , 1998 ). In particular, in the Cassagna mine some of these rare minerals (such as medaite, palenzonaite, strontiopiemontite, sursassite, tinzenite, and tiragalloite) were found. In this paper we report the occurrence...

... . Gramaccioli C.M. Liborio G. Pilati T. ( 1981 ): Structure of medaite, Mn 6 [VSi 5 O 18 (OH)]: the presence of a new kind of heteropolysilicate anion . Acta. Cryst. , 37 , 1972 – 1978 . Groat L.A. Evans R.J. Cempirek J. McCammon C. Houzar S. ( 2013 ): Fe-rich...

..., northern Apennines, Italy, a complex network of veins and fractures allowed the formation of a great variety of rare and new minerals; among these, vanadium minerals, as saneroite, medaite, palenzonaite, gamagarite, volborthite, tangeite, reppiaite, and vanadomalayaite ( Basso et al. , 1994...

... in data stems from the fact that arsenic is a major component of only a small number of mostly unusual silicate minerals. These include medaite, (Mn,Ca) 6 (V,As)Si 5 O 18 (OH) ( Gramaccioli et al. 1981 ), and ardennite, (Mn,Ca,Mg) 4 (Al,Mg,Fe) 6 (V,As)Si 5 O 22 (OH) 6 ( Donnay and Allmann 1968 ), where...

... and chemical data X-ray powder pattern crystal structure TEM analysis A great variety of rare and new minerals have been found in the manganese ore deposits of the Val Graveglia, Northern Apennines, eastern Liguria, Italy. Some of them are vanadium minerals such as saneroite, medaite, palenzonaite...

... ) are compatible with a Si–V substitution (values of 1.68–169 Å are usually found for saneroite, Nagashima and Armbruster, 2010 a , c ; 1.70 Å for medaite, Nagashima and Armbruster, 2010 b ). Note that, besides the chemical strain due to a three component solid solution, T (6) is not the most distorted 4...

... Belmonte, Cristina Carbone, Roberto Cabella, Federica Zaccarini and Corrado Balestra *E-mail: cristian.biagioni@unipi.it The As analogue of medaite Monoclinic: P 2 1 / n ; structure determined a = 6.7099(3), b = 29.001(1), c = 7.5668(3) Å, β = 95.469(3)° 4.777(58), 3.266(100), 3.159...