Clino-suenoite, a newly approved magnesium-iron-manganese amphibole from Valmalenco, Sondrio, Italy

• Published in: Mineralogical magazine Vol. 82; no. 1; pp. 189 - 198
• Main Authors: Oberti, Roberta, Boiocchi, Massimo, Hawthorne, Frank C, Ciriotti, Marco E, Revheim, Olav, Bracco, Roberto
• Format: Journal Article
• Language: English
• Published: London Mineralogical Society 01.02.2018; Cambridge University Press
• Subjects: alkaline earth metals; amphibole group; braunite; Carbonates; chain silicates; clinosuenoite; coexisting minerals; crystal chemistry; Crystal structure; electron probe data; Europe; formula; garnet group; Glaciers; iron; Italy; lattice parameters; Lombardy Italy; Magnesium; Malenco Valley; Manganese; metals; metamorphic rocks; Mineralization; Mineralogy; nesosilicates; new minerals; orthosilicates; quartzites; rhodonite; rhodonite group; Scerscen Glacier; silicates; Sondrio Italy; Southern Europe; space groups; spessartine; suenoite; Symmetry; unit cell; X-ray diffraction; X-ray diffraction data; Canada; Italy
• ISSN: 0026-461X; 1471-8022
• DOI: 10.1180/minmag.2017.081.034

Clino-suenoite, ideally ∎Mn22+ Mg5Si8O22(OH)2 is a new amphibole of the magnesium-iron-manganese subgroup of the amphibole supergroup. The type specimen was found at the Lower Scerscen Glacier, Valmalenco, Sondrio, Italy, where it occurs in Mn-rich quartzite erratics containing braunite, rhodonite, spessartine, carbonates and various accessory minerals. The empirical formula derived from electron microprobe analysis and single-crystal structure refinement is: ANa0.04B(Mn1.582+ Ca0.26Na0.16)Σ2.00C(Mg4.21Mn0.612+ Fe0.042+ Zn0.01Ni0.01Fe0.083+ Al0.04)Σ5.00TSi8.00O22W[(OH1.94F0.06)]Σ=2.00. Clino-suenoite is biaxial (+), with α = 1.632(2), β = 1.644(2), γ = 1.664(2) and 2Vmeas. = 78(2)° and 2Vcalc. = 76.3°. The unit-cell parameters in the C2/m space group are a = 9.6128(11), b = 18.073(2), c = 5.3073(6) Å, β = 102.825(2)° and V = 899.1(2) Å3 with Z = 2. The strongest ten reflections in the powder X-ray diffraction pattern [d (in Å), I, (hkl)] are: 2.728, 100, (151); 2.513, 77, (202); 3.079, 62, (310); 8.321, 60, (110); 3.421, 54, (131); 2.603, 42, (061); 2.175, 42, (261); 3.253, 41, (240); 2.969, 40, (221); 9.036, 40, (020).