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 %):
Zonal and sectorial monazite (Ce) crystals from ceramic granite pegmatites of the Adui pluton are enriched in Ce and La, whereas monazite from the miarolitic gemstone pegmatites at the western contact of the pluton are enriched in Nd, Sm, Gd, and Y. This difference is caused by earlier crystallization of ceramic pegmatites and higher temperatures of their formation (650-600°C for ceramic pegmatites and 550-300°C for miarolitic pegmatites). Monazites from ceramic and miarolitic pegmatites of the Adui pluton differ in La and Nd contents, but their compositional trend in La-Nd coordinates is similar to the variation in monazite composition from the early to late granite pegmatites in the Ilmeny Mountains. It is suggested that decrease in temperature is a factor controlling REE contents in monazite. Heterovalent P Si and REE Th, Ca isomorphism in the consecutive zones of growth pyramids in monazite is both unidirectional and wave like. Monazite from granite pegmatites of the Adui pluton and Ilmeny Mountains crystallized mainly under slightly alkaline conditions.
Stibiomicrolite has been identified in the Lepidolite Vein (53°06.8′N, 60°15.4′E) as metasomatic veinlets with tantite replacing stibiotantalite along fractures. The mineral is light gray yellow, isotropic, and with reflectance of ~12%. The average chemical composition of two stibiomicrolite samples is as follows, wt %: Sb 2 O 3 23.34, CaO 4.91, Na 2 O 0.96, MnO 0.17, Ta 2 O 5 58.97, Nb 2 O 5 6.64, total 94.99; H 2 O calc 3.4. The empirical formula is (Sb 1.02 Ca 0.55 Na 0.20 Mn 0.02 ) 1.79 (Ta 1.68 Nb 0.32 ) 2.0 O 6 (OH) 1.18 . Trilithionite, polylithionite, albite, manganotantalite, beryl (goshenite), elbaite, stibiotantalite, and tantite are associated with stibiomi crolite in the central zone of the Lepidolite Vein.
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