Informace o publikaci

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


BOSI Ferdinando BIAGIONI Cristian PEZZOTTA Federico SKOGBY Henrik HALENIUS Ulf CEMPÍREK Jan HAWTHORNE Frank C. LUSSIER Aaron J. ABDU Yassir A. DAY Maxwell C. FAYEK Mostafa CLARK Christine M. GRICE Joel D. HENRY Darrell J.

Rok publikování 2022
Druh Článek v odborném periodiku
Časopis / Zdroj Mineralogical Magazine
Fakulta / Pracoviště MU

Přírodovědecká fakulta

Klíčová slova uvite; new mineral species; tourmaline; crystal-structure refinement; electron microprobe; Mössbauer spectroscopy; infrared spectroscopy; optical absorption spectroscopy
Popis Uvite, CaMg3(Al5Mg)(Si6O18)(BO3)(3)(OH)(3)(OH), is a new mineral of the tourmaline supergroup. It occurs in the Facciatoia quarry, San Piero in Campo, Elba Island, Italy (42 degrees 45' 04.55 '' N, 10 degrees 12'50.89 '' E) at the centre of a narrow (2-3 cm wide) vein composed of aggregates of dark brown to black tourmaline, penetrating (magnesite + dolomite)-rich hydrothermally altered metaserpentinite. Crystals are euhedral and up to 1 cm in size, brown with a vitreous lustre, conchoidal fracture and grey streak. Uvite has a Mohs hardness of similar to 7 1/2, a calculated density of 3.115 g/cm(3) and is uniaxial (-). Uvite has trigonal symmetry, space group R3m, a = 15.9519(10) angstrom, c = 7.2222(5) angstrom, V = 1597.3(1) angstrom 3 and Z = 3. The crystal structure was refined to R-1 = 1.77% using 1666 unique reflections collected with MoKa X-rays. Crystal-chemical analysis resulted in the empirical crystal-chemical formula (X)(Ca(0.61)Na(0.35)A(0.04)) S1.00Y Mg1.50Fe0.472+Al0.71Fe3+similar to 0.14Ti(0.1)8 similar to S3.00 Z Al4.54Fe0.183+V3+similar to 0.02 Mg-1.27) S-6.00 T Si5.90Al0.10()similar to S6.00O18 similar to BO3() 3O(3)(OH) 3O(1)[(OH)(0.55)F0.05O0.40] S1.00 which recast in its ordered form for classification purposes is: Uvite is a hydroxy-species belonging to the calcic-group of the tourmaline supergroup. The closest end-member compositions of valid tourmaline species are fluor-uvite and feruvite, to which uvite is related by the substitutions W(OH)-. WF- and YMg2+. YFe2+, respectively. The occurrence of a solid-solution between uvite and magnesio-lucchesiite, according to the substitution ZMg2+ + W(OH)-. ZAl(3+) + WO2-, is supported by experimental data. The new mineral was approved by the IMA-CNMNC (IMA 2019-113). Uvite from Facciatoia formed by the reaction between B-rich fluids, released during the crystallisation process of LCT pegmatites, and the surrounding metaserpentinites, altered by contact metamorphism in the aureole of the Miocene Mt. Capanne monzogranitic pluton.

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