Non-metamict aeschynite-(Y), polycrase-(Y), and samarskite-(Y) in NYF pegmatites from arvogno, vigezzo valley (central alps, Italy)

At Arvogno, Vigezzo valley in the Central Alps, Italy, pegmatite dikes are unique in the scenario of a tertiary alpine pegmatite field because they show marked geochemical and mineralogical niobium–yttrium–fluorine features. These pegmatites contain AB 2 O 6 aeschynite group minerals and ABX 2 O 8 euxenite group minerals as typical accessory minerals including aeschynite-(Y), polycrase-(Y), and samarskite-(Y). They are associated with additional typical minerals such as fluorite, Y-dominant silicates, and xenotime-(Y). The Y–Nb–Ti–Ta AB 2 O 6 and ABX 2 O 8 oxides at the Arvogno pegmatites did not exhibit any textural and compositional features of oxidation or weathering. They are characterized by low self-radiation-induced structural damage, leading to the acquisition of unit-cell data for aeschynite-(Y), polycrase-(Y), and samarskite-(Y) by single-crystal X-ray diffraction. Aeschynite-(Y) and polycrase-(Y) crystals allowed for both to provide space groups whereas samarskite-(Y) was the first crystal from pegmatites for which cell-data were obtained at room temperature but did not allow for the accurate determination of the space group. According to the chemical compositions defined by Ti-dominant content at the B-site, the cell parameters, respectively, corresponded to polycrase-(Y), aeschynite-(Y), and the monoclinic cell of samarskite-(Y). Emplacement of Alpine pegmatites can be related to the progressive regional metamorphic rejuvenation from east to west in the Central Alps, considering the progressive cooling of the thermal Lepontine Barrovian metamorphic dome. Previous studies considered magmatic pulses that led to emplace the pegmatite field in the Central Alps. As an example, the pegmatites that intruded the Bergell massif were aged at 28–25 millions of years or younger, around 20–22 m.y

Deveroite-(Ce): A new REE-oxalate from Mount Cervandone, Devero Valley, Western-Central Alps, Italy

AbstractDeveroite-(Ce), ideally Ce2(C2O4)3·10H2O, is a new mineral (IMA 2013-003) found in the alpine fissures of Mount Cervandone, overlooking the Devero Valley, Piedmont, Italy. It occurs as sprays of colourless elongated tabular, acicular prisms only on cervandonite-(Ce). It has a white streak, a vitreous lustre, is not fluorescent and has a hardness of 2–2.5 (Mohs' scale). The tenacity is brittle and the crystals have a perfect cleavage along {010}. The calculated density is 2.352 g/cm3. Deveroite-(Ce) is biaxial (–) with 2V of ∼77°, is not pleochroic and the extinction angle (β ∧ c) is ∼27°. No twinning was observed. Electron microprobe analyses gave the following chemical formula: (Ce1.01Nd0.33La0.32Pr0.11Y0.11Sm0.01Pb0.04U0.03Th0.01Ca0.04)2.01(C2O4)2.99·9.99H2O. Although synchrotron radiation was not used to solve the structure of deveroite-(Ce) the extremely small size of the sample (13 μm × 3 μm × 1 μm) did not allow us to obtain reliable structural data. However, it was possible to determine the space group (monoclinic, P21/c) and the unit-cell parameters, which are: a = 11.240(8) Å, b = 9.635(11) Å, c = 10.339(12) Å, β = 114.41(10)°, V = 1019.6 Å3. The strongest lines in the powder diffraction pattern [d in Å (I)(hkl)] are: 10.266(100)(100); 4.816(35.26)(21); 3.415(27.83)(300); 5.125(24.70)(200); and 4.988(22.98)(111). Deveroite-(Ce) is named in recognition of Devero valley and Devero Natural Park.</jats:p

Prevalence of stratified epithelium-specific antinuclear antibodies in 138 patients with lichen planus

BACKGROUND: Antibodies to stratified epithelia characterize chronic ulcerative stomatitis, an entity that very closely resembles erosive lichen planus both clinically and histologically. These antibodies are directed against a 70-kd antigen. OBJECTIVE: Our aim was to verify whether antibodies to stratified epithelia are present in patients with common lichen planus. PATIENTS AND METHODS: One hundred thirty-eight patients with various forms of lichen planus were studied. Indirect immunofluorescence was performed on both monkey esophagus and HEp2-2000 cells. Immunoblotting was done with cultured keratinocytes used as the source antigen. RESULTS: Nineteen patients had antibodies to stratified epithelia (in 9 directed against an antigen of 70 kd). Forty-eight patients had circulating antibodies detected by indirect immunofluorescence on both monkey esophagus and HEp2-2000 cells (in 7 directed against an antigen of 70 kd). Indirect immunofluorescence was positive only on HEp2-2000 cells in 21 patients. Indirect immunofluorescence was negative in 50 patients on both HEp2-2000 cells and monkey esophagus. None of the last 71 patients had antibodies directed to an antigen of 70 kd. LIMITATIONS: This is a serological study; results from direct immunofluorescence studies would be interesting. CONCLUSION: Antibodies to stratified epithelia directed to an antigen of 70 kd are not exclusive to chronic ulcerative stomatitis, but are also present in some patients with lichen planus