Florencite-(Sm)—(Sm,Nd)Al3(PO4)2(OH)6: A new mineral species of the alunite-jarosite group from the subpolar urals

Abstract

Florencite (Sm), a new mineral species of the florencite subgroup, was found in association with xenotime (Y) in quartz veins of the Maldynyrd Range of the Subpolar Urals as thin zones within rhombohe dral crystals of florencite (Ce) with faceting by {01 1} and {10 2}. The thickness of particular florencite (Sm) zones is 0.01-0.1 mm, and the total thickness of a series of such zones is 1-3 mm. Florencite (Sm) is colorless and pale pink or pale yellow with white streaks; its Mohs hardness is 5.5-6.0. Its measured and cal culated densities are 3.70 and 3.743 g/cm 3 , respectively. The mineral is transparent, nonpleochroic, and uniaxial (positive), and ω = 1.704(2) and ε = 1.713(2). The electron beam's fluorescence spectrum was 592 nm (intense green luminescence of Sm 3+ ) and 558 nm (yellow luminescence of Nd 3+ ). The chemical composi tion was as follows (microprobe, average of 2 WDS, wt %):

Graulichite-(La), LaFe<sup>3+</sup><sub>3</sub>(AsO<sub>4</sub>)<sub>2</sub>(OH)<sub>6</sub>, a new addition to the alunite supergroup from the Patte d'Oie mine, Bou Skour mining district, Morocco

“…Similar features can be noted in the infrared spectrum of florencite-(La) reported by Frost et al (2013) but not discussed. In addition, similar bands occur in the Raman spectrum of florencite-(La) reported by Repina et al (2011). These authors interpreted the band at 2957 cm −1 as due to O-H stretching, whereas the bands in the region between 1400 and 1500 cm −1 are interpreted as due to the presence of CO 3 groups.…”

Rare earth mineral diversity controlled by REE pattern shapes

“…These anomalies require distinct geochemical conditions, either F-rich fluids (Loges et al , 2013) or coexistence of fluorite for Y anomalies (Chebotarev et al , 2019), and oxidising conditions coupled with low temperatures for Ce anomalies (Anenburg et al , 2018; Burnham and Berry, 2014; Sørensen, 1976). The small Sm-dominant zones inside florencite grains reported by Repina et al (2011) require exceptional formation conditions (Repina et al , 2014). Therefore, ‘one paragenetic mode’ cannot account for the entire diversity observed in REE mineral name suffixes, and they do not represent ‘a single natural kind’ (also remembering that the ‘natural kind’ concept and mineralogy are incompatible; Santana, 2019).…”

“…Coloured lines indicate the field boundaries for dominant Sm (red and blue) and Yb (all others). Data sources: Masau et al (2002), Repina et al (2011), Voloshin et al (1984), Voloshin et al (1983), Simmons et al (2006) and Buck et al (1999). …”

“…Insofar as nomenclature is inevitably subjective, it could be hard to justify naming a new mineral species. For example, instances of florencite-(Sm) described by Repina et al (2011) are not individual grains, but rather Sm-dominated thin growth zones inside florencite-(Ce). Hazen (2019) argued that the diversity of REE minerals is an artificial construct by the IMA–CNMNC mineral names rules.…”

Indicação química de possível ocorrência de Florencita-(Y) em Bom Sucesso (Minas Gerais, Brasil)

“…A florencita (nome em homenagem ao mineralogista brasileiro William Florence, 1864-1942, que fez o exame químico preliminar da primeira florencita) é um fostato de elementos terras-raras leves deste supergrupo, no qual o sítio D foi até agora descrito como predominantemente ocupado por Ce, La, Nd ou Sm, com Al no sítio G (Repina et al 2011). As diferentes espécies de florencita conhecidas cristalizam-se no sistema trigonal (classe escalenoédrica hexagonal), fazem parte do grupo da plumbogummita [PbAl 3 (PO 3.5 (OH) 0.5 ) 2 (OH) 6 ] (Mills et al 2009) e seus termos extremos estão listados na Tab.…”