Details

Autor(en) / Beteiligte

• Kampf, Anthony R.
• Plášil, Jakub
• Nash, Barbara P.
• Marty, Joe

Titel

Ammoniomathesiusite, a new uranyl sulfate–vanadate mineral from the Burro mine, San Miguel County, Colorado, USA

Ist Teil von

• Mineralogical magazine, 2019-02, Vol.83 (1), p.115-121

Ort / Verlag

London: Cambridge University Press

Erscheinungsjahr

2019

Quelle

Alma/SFX Local Collection

Beschreibungen/Notizen

• Abstract The new mineral ammoniomathesiusite (NH 4 ) 5 (UO 2 ) 4 (SO 4 ) 4 (VO 5 )·4H 2 O, was found in the Burro mine, San Miguel County, Utah, USA, where it occurs as a secondary phase on asphaltum/quartz matrix in association with ammoniozippeite, gypsum, jarosite and natrozippeite. The mineral forms pale yellow to greenish-yellow prisms, up to ~0.3 mm long, with pale-yellow streak and bright yellow–green fluorescence. Crystals are transparent and have vitreous lustre. The mineral is brittle, with Mohs hardness of 2½, stepped fracture and two cleavages: excellent on {110} and good on {001}. The calculated density is 3.672 g/cm 3 . Ammoniomathesiusite is optically uniaxial (–) with ω = 1.653(2) and ε = 1.609(2) (white light). Pleochroism is: O = green-yellow, E = colourless; O > E . Electron microprobe analyses yielded the empirical formula [(NH 4 ) 4.75 (UO 2 ) 4 (SO 4 ) 4 (VO 5 )·4(H 2.07 O). The five strongest powder X-ray diffraction lines are [ d obs Å( I )( hkl )]: 10.57(46)(110), 7.10(62)(001), 6.41(100)(101), 3.340(35)(240) and 3.226(44)(141). Ammoniomathesiusite is tetragonal, P 4/ n with a = 14.9405(9), c = 7.1020(5) Å, V = 1585.3(2) Å 3 and Z = 2. The structure of ammoniomathesiusite ( R 1 = 0.0218 for 3427 I > 2σ I ) contains heteropolyhedral sheets based on [(UO 2 ) 4 (SO 4 ) 4 (VO 5 )] 5– clusters. The structure is identical to that of mathesiusite, with ${\rm NH}_{\rm 4}^{\rm +} $ in place of K + .