Crystal-chemical relations and classification problems in tourmalines belonging to the oxy-schorl–oxy-dravite–bosiite–povondraite series

Mn-bearing purplish-red tourmaline from the Anjanabonoina pegmatite, Madagascar

“…With the exception of the broad absorption band at ∼9500 cm -1 , the characteristics (band energy, band width and polarisation) of all observed bands in the spectra of the present sample are in very good agreement with those recorded for Mn 3+ -bearing tourmaline specimens (Reinitz and Rossman, 1988;Ertl et al, 2005;Novák et al, 2013;Bosi et al, 2017a). In agreement with these previously published studies we assign bands at 21,950, 19,800, ∼18,000, 13,500 cm -1 to electronic transitions in octahedrally coordinated Mn 3+ and the very weak and sharp band at 24,330 cm -1 to an electronic transition in octahedrally coordinated Mn 2+ .…”

Chromium-rich vanadio-oxy-dravite from the Tzarevskoye uranium–vanadium deposit, Karelia, Russia: a second world-occurrence of Al–Cr–V–oxy-tourmaline

“…The plotted data in these diagrams (for a total 109 data sets) are from: Peltola et al (1968); Foit and Rosenberg (1979); Nuber and Schmetzer (1979); Rumyantseva (1983); Gorskaya et al (1987, 1989); Cavarretta and Puxeddu (1990); Grice et al (1993); Grice and Ercit (1993); Ẑàĉek et al 2000; Bosi et al (2004, 2012, 2013a,b, 2014a,b, 2017a,b); Ertl et al (2008, 2016); Arif et al (2010), in which Fe was considered +3 as suggested by the authors; Baksheev et al (2011); Lupulescu and Rowe (2011); Rozhdestvenskaya et al (2011); Cempírek et al (2013); Reznitskii et al (2014) and Vereshchagin et al (2014).…”

“…Oxy-tourmalines rich in both V and Cr are unusual minerals and occur almost exclusively in metamorphosed V- and Cr-enriched host rocks such as sulfide-rich black shales, graphite quartzites and calcareous metasediments (Snetsinger, 1966; Kazachenko et al , 1993; Bačik et al , 2011; Cempírek et al , 2013). Most oxy-tourmalines with dominant V and/or Cr (V 2 O 3 or Cr 2 O 3 > 9 wt.%) were found in the Sludyanka crystalline complex, Lake Baikal, Russia (Bosi et al , 2004, 2012, 2013a,b; Reznitskii et al , 2014; Bosi et al , 2014a,b, 2017a,b). Among these is a vanadio-oxy-dravite, ideally NaV 3 (Al 4 Mg 2 )(Si 6 O 18 )(BO 3 ) 3 (OH) 3 O, a rare tourmaline recently described by Bosi et al (2014a).…”

Petrogenetic controls on the origin of tourmalinite veins from Mandrolisai igneous massif (central Sardinia, Italy): Insights from tourmaline crystal chemistry

“…Although this empirical formula would correspond to a schorl (Fe 2+ > Mg at the Y site), on the basis of the structural formula derived from the procedure of Henry et al (2011) for hydroxy-tourmalines sample BUP4 was named dravite as the total of Mg is higher than Fe 2+ (Table 2). This is another example of ambiguity in the tourmaline nomenclature, derived by naming tourmaline species by using either the empirical or the calculated formula (for further details see Bosi et al, 2017b;Bosi, 2018).…”