Uvite, CaMg₃(Al₅Mg)(Si₆O₁₈)(BO₃)₃(OH)₃(OH), a new, but long-anticipated mineral species of the tourmaline supergroup from San Piero in Campo, Elba Island, Italy

Abstract Uvite, CaMg 3 (Al 5 Mg)(Si 6 O 18 )(BO ) (OH) (OH), is a new mineral of the tourmaline supergroup. It occurs in Facciatoia quarry, San Piero Campo, Elba Island, Italy (42°45?04.55?N, 10°12?50.89?E) at centre narrow (2–3 cm wide) vein composed aggregates dark brown to black tourmaline, penetrating (magnesite + dolomite)-rich hydrothermally altered metaserpentinite. Crystals are euhedral and up 1 size, with vitreous lustre, conchoidal fracture grey streak. Uvite has Mohs hardness ~7½, calculated density 3.115 g/cm uniaxial (–). trigonal symmetry, space group R m , = 15.9519(10) Å, c 7.2222(5) V 1597.3(1) Å Z 3. The crystal structure was refined 1.77% using 1666 unique reflections collected Mo K ? X-rays. Crystal-chemical analysis resulted empirical crystal-chemical formula $^X ({\rm Ca}_{0.61}{\rm Na}_{{0.35}} \square_{{0.04}})_{\Sigma 1.00}{}^{Y} \left( {{\rm Mg}_{1.50}{\rm Fe}^{2 }_{0.47} {\rm Al}_{0.71}{\rm Fe}^{3 }_{0.14} Ti}_{0.18}} \right)_{\Sigma 3.00}$ ${}^{Z} Al}_{4.54}{\rm }_{0.18} V}^{3 }_{0.02} Mg}_{1.27}} 6.00}{}^{T}\left[ {{\left( Si}_{5.90}{\rm Al}_{0.10}} \right)}_{\Sigma 6.00}{\rm O}_{18}} \right]{\rm } BO_3} \right)_3^{} {^{\rm O(3)}}\left( OH} \right)_3{}^{{\rm O}\left( \right)} [\left( \right)_{0.55}{\rm F}_{0.05}{\rm O}_{0.40}]_{\Sigma 1.00}$ which recast its ordered form for classification purposes is: $$\eqalign{& ^{\rm X} Na}_{0.35}\squ _{0.04})_{\Sigma 1.00}{}^{\rm Y} Mg}_{2.35}{\rm 3.00} \cr & {}^{\rm Z} Al}_{5.25}{\rm }_{0.32} Mg}_{0.42}} 6.00}{}^{\rm T} \left[ }\left( \right)_3{}^{\rm V} W} 1.00}}$$ hydroxy-species belonging calcic-group closest end-member compositions valid species fluor-uvite feruvite, uvite related by substitutions W – ? F Y Mg 2+ Fe respectively. occurrence solid-solution between magnesio-lucchesiite, according substitution Al 3+ 2– supported experimental data. approved IMA–CNMNC (IMA 2019-113). from formed reaction B-rich fluids, released during crystallisation process LCT pegmatites, surrounding metaserpentinites, contact metamorphism aureole Miocene Mt. Capanne monzogranitic pluton.