IMA 2015-097 = alwilkinsite-(Y)

[Marco E. Ciriotti]

Prossima pubblicazione.

Referenza:
▪ Kampf, A.R., Plášil, J., Čejka, J., Marty, J., Škoda, R., Lapčák, L. (2017): Alwilkinsite-(Y), a new rare-earth uranyl sulfate mineral from the Blue Lizard mine, San Juan County, Utah, USA. Mineralogical Magazine, 81, (in press).

Abstract:
The new mineral alwilkinsite-(Y) (IMA2015-097), Y(H2O)7[(UO2)3(SO4)2O(OH)3]·7H2O, was found in the Blue Lizard mine, San Juan County, Utah, USA, where it occurs as secondary alteration phases. The mineral is slightly flexible before brittle failure with splintery fracture and perfect cleavage parallel to [010], has Mohs hardness of about 2–2½, exhibits dull greenish-gray fluorescence and has a calculated density of 3.371 g·cm-3. Alwilkinsite-(Y) occurs as yellowish-green needles, elongate on [010], with domatic terminations and exhibits the forms {102}, {301} and {12-4}. It is optically biaxial (+) with α = 1.573(1), β = 1.581(1), γ = 1.601(1) (white light), the measured 2V is 65.3(1)°, the dispersion is r < v (weak), the optical orientation is X = c, Y = a, Z = b and there is no pleochroism. Electron microprobe analyses yielded the empirical formula (Y0.66Dy0.08Gd0.06Er0.05Nd0.03Yb0.03Sm0.02Ce0.01)Σ0.94(H2O)7[(UO2)3(S1.01O4)2O(OH)3]·7H2O. The eight strongest X-ray powder diffraction lines are [dobs Å(I)(hkl)]: 9.88(100)(101,002), 7.47(13)(102), 5.621(17)(103,201), 4.483(18)(104), 3.886(14)(130,222), 3.322(46)(multiple), 3.223(13)(multiple) and 3.145(16)(034). Alwilkinsite-(Y) is orthorhombic, P212121, a = 11.6194(5), b = 12.4250(6), c = 19.4495(14) Å, V = 2807.9(3) Å3 and Z = 4. The structure of alwilkinsite-(Y) (R1 = 0.042 for 4244 Fo > 4σF) contains edge-sharing chains of uranyl bipyramids with outlying sulfate tetrahedra that are similar to the chain linkages within the uranyl sulfate sheets of the zippeite structure. Short segments of the uranyl sulfate chains in the alwilkinsite-(Y) structure have the same topology as portions of the uranyl sulfate linkages in uranopilite. Alwilkinsite-(Y) is named for Alan (Al) J. Wilkins, MD (born 1955), the discoverer of the mineral.

[Marco E. Ciriotti]

Pubblicazione avvenuta.

Referenza:
▪ Kampf, A.R., Plášil, J., Čejka, J., Marty, J., Škoda, R., Lapčák, L. (2017): Alwilkinsite-(Y), a new rare-earth uranyl sulfate mineral from the Blue Lizard mine, San Juan County, Utah, USA. Mineralogical Magazine, 81, 895-907.

Abstract:
The new mineral alwilkinsite-(Y) (IMA2015-097), Y(H2O)7[(UO2)3(SO4)2O(OH)3]·7H2O, was found in the Blue Lizard mine, San Juan County, Utah, USA, where it occurs as secondary alteration phases. The mineral is slightly flexible before brittle failure with splintery fracture and perfect cleavage parallel to [010], has Mohs hardness of about 2–2½, exhibits dull greenish-gray fluorescence and has a calculated density of 3.371 g·cm-3. Alwilkinsite-(Y) occurs as yellowish-green needles, elongate on [010], with domatic terminations and exhibits the forms {102}, {301} and {12-4}. It is optically biaxial (+) with α = 1.573(1), β = 1.581(1), γ = 1.601(1) (white light), the measured 2V is 65.3(1)°, the dispersion is r < v (weak), the optical orientation is X = c, Y = a, Z = b and there is no pleochroism. Electron microprobe analyses yielded the empirical formula (Y0.66Dy0.08Gd0.06Er0.05Nd0.03Yb0.03Sm0.02Ce0.01)Σ0.94(H2O)7[(UO2)3(S1.01O4)2O(OH)3]·7H2O. The eight strongest X-ray powder diffraction lines are [dobs Å(I)(hkl)]: 9.88(100)(101,002), 7.47(13)(102), 5.621(17)(103,201), 4.483(18)(104), 3.886(14)(130,222), 3.322(46)(multiple), 3.223(13)(multiple) and 3.145(16)(034). Alwilkinsite-(Y) is orthorhombic, P212121, a = 11.6194(5), b = 12.4250(6), c = 19.4495(14) Å, V = 2807.9(3) Å3 and Z = 4. The structure of alwilkinsite-(Y) (R1 = 0.042 for 4244 Fo > 4σF) contains edge-sharing chains of uranyl bipyramids with outlying sulfate tetrahedra that are similar to the chain linkages within the uranyl sulfate sheets of the zippeite structure. Short segments of the uranyl sulfate chains in the alwilkinsite-(Y) structure have the same topology as portions of the uranyl sulfate linkages in uranopilite. Alwilkinsite-(Y) is named for Alan (Al) J. Wilkins, MD (born 1955), the discoverer of the mineral.

[Marco E. Ciriotti]

A second world occurrence.

Reference:
▪ Campostrini, I. (2017): Alwilkinsite-(Y): secondo ritrovamento mondiale nel giacimento uranifero di Limes, Val Daone, Trento. Micro, 15, 92-95.

Abstract:
Alwilkinsite-(Y) (IMA 2015-097) is an yttrium and uranyl sulfate, recently discovered in the Blue Lizard Mine galleries, Red Canyon, White Canyon
District, San Juan County, Utah, USA (Kampf et al., 2016). The second world occurrence of alwilkinsite-(Y) is from Limes, Val Daone Mine, Trentino- Alto Adige, Italy, The mineral forms lemon yellow aggregates of acicular crystals up to 1 mm, deposited on a sandstone matrix, in association
with gypsum, johannite and zippeite. Unit cell parameters were obtained refining powder data: orth. P212121 a 11.583(1), b 12.428(1), c 19.363(3) Å; V 2787.3(4) Å3.