Informace o publikaci

Princivalleite, Na(Mn2Al)Al6(Si6O18)(BO3)3(OH)3O, a new mineral species of the tourmaline supergroup from Veddasca Valley, Varese, Italy

Logo poskytovatele
Autoři

BOSI Ferdinando PEZZOTTA Federico SKOGBY Henrik ALTIERI Alessandra HALENIUS Ulf TEMPESTA Gioacchino CEMPÍREK Jan

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

Přírodovědecká fakulta

Citace
www https://www.cambridge.org/core/journals/mineralogical-magazine/article/princivalleite-namn2alal6si6o18bo33oh3o-a-new-mineral-species-of-the-tourmaline-supergroup-from-veddasca-valley-varese-italy/FB93F3A23A690F8422BFFDCADFB096F2
Doi http://dx.doi.org/10.1180/mgm.2022.3
Klíčová slova princivalleite; new mineral species; crystal-structure refinement; electron microprobe; Mossbauer spectroscopy; infrared spectroscopy; optical absorption spectroscopy; micro-laser induced breakdown spectroscopy
Popis Princivalleite, Na(Mn2Al)Al6(Si6O18)(BO3)3(OH)3O, is a new mineral (IMA2020-056) of the tourmaline supergroup. It occurs in the Veddasca Valley, Luino area, Varese, Lombardy, Italy (46°03’30.74’’N, 8°48’24.47’’E) at the centre of a narrow (2–3 cm wide) vertical pegmatitic vein, a few metres long, crosscutting a lens of flaser gneiss. Crystals are subhedral (up to 10 mm in size), azure with a vitreous lustre, conchoidal fracture and white streak. Princivalleite has a Mohs hardness of ~7, a calculated density of 3.168 g/cm3 and is uniaxial (–). Princivalleite has trigonal symmetry, space group R3m, a = 15.9155(2) A, c = 7.11660(10) A, V = 1561.15(4) A3 and Z = 3. The crystal structure was refined to R1 = 1.36% using 1758 unique reflections collected with MoK? X-ray intensity data. Crystal-chemical analysis resulted in the empirical crystal-chemical formula X(Na0.54Ca0.11?0.35)?1.00Y(Al1.82Mn2+0.84Fe2+0.19Zn0.07Li0.08)?3.00Z(Al5.85Fe2+0.13Mg0.02)?6.00[T(Si5.60Al0.40)?6.00O18](BO3)3O(3)[(OH)2.71O0.29]?3.00O(1)[O0.66F0.22(OH)0.12]?1.00 which recast in its ordered form for classification purposes is: X(Na0.54Ca0.11?0.35)?1.00 Y(Al1.67Mn2+0.84Fe2+0.32Zn0.07Mg0.02Li0.08)?3.00 ZAl6.00[T(Si5.60Al0.40)?6.00O18](BO3)3V[(OH)2.71O0.29]?3.00W[O0.66F0.22(OH)0.12]?1.00. Princivalleite is an oxy-species belonging to the alkali group of the tourmaline supergroup. The closest end-member compositions of valid tourmaline species are those of oxy-schorl and darrellhenryite, to which princivalleite is related by the substitutions Mn2+ - Fe2+ and Mn2+ - 0.5Al3+ + 0.5Li+, respectively. Princivalleite from Veddasca Valley is a geochemical anomaly, originated in a B-rich and peraluminous anatectic pegmatitic melt formed in situ, poor in Fe and characterised by reducing conditions in the late-stage metamorphic fluids derived by the flaser gneiss. The Mn-enrichment in this new tourmaline is due to absence of other minerals competing for Mn such as garnet.
Související projekty:

Používáte starou verzi internetového prohlížeče. Doporučujeme aktualizovat Váš prohlížeč na nejnovější verzi.

Další info