Redcanyonite, (NH4)2Mn[(UO2)4O4(SO4)2](H2O)4, a new zippeite group mineral from the Blue Lizard Mine, San Juan County, Utah, USA

Redcanyonite (IMA2016-082), (NH4)2Mn[(UO2)4O4(SO4)2](H2O)4, occursunderground in the Blue Lizard mine, Red Canyon, White Canyon district,San Juan County, Utah, USA. It occurs with natrozippeite, brochantite, devilline, posnjakite, johannite, gypsum, bobcookite, pickingerite, pentahydrite, and the NH4-analog of zippeite, ammoniozippeite. Redcanyonite occurs as radial aggregates of red-orange needles and blades individually reaching up to 0.2 mm in length, with aggregates measuring up to 1 mm in diameter. Crystals are flattened on {010} and elongated along [100], exhibit perfect cleavage on {010}, and exhibit the forms {010}, {001}, {101}, and {10-1}. Twinning is ubiquitous, by 180° rotation on [100]. Redcanyonite is translucent with a pale orange streak, is nonfluorescent, has a hardness of 2 (Mohs), and has brittle tenacity with uneven fracture. Optically, redcanyonite is biaxial (+), α = 1.725(3), β = 1.755(3), γ = 1.850(5) (white light); 2V (meas.) = 60(2)°, 2V (calc.) = 61.3°; dispersion is r < v, very strong. Pleochroism: X = orange, Y = yellow, and Z = orange; Y << X < Z. The optical orientation is X = b, Y ≈ c*, Z ≈ a. Theempirical formula is (NH4)2.02(Mn0.49Cu0.09Zn0.06)Σ0.64H + 0.72[(UO2)4O4(S0.99P0.01O4)2](H2O)4, based on 4 U and 24 O apfu. Redcanyonite is monoclinic, C2/m, a = 8.6572(17), b = 14.155(3), c = 8.8430(19) Å, β = 104.117(18)°, V = 1050.9(4) Å 3 and Z = 2. The structure was refined to R1 = 0.0382 for 1079 reflections with Iobs > 3σI. Uranyl oxo-sulfate sheets in redcanyonite adopt the well-known zippeite topology, which consists of zig-zag chains of uranyl pentagonal bipyramids linked by sulfate tetrahedra to form sheets. The sheets are linked to each other through bonds to interlayer NH4 + groups and octahedrally coordinated Mn2+, and by hydrogen-bonds from H2O groups. Redcanyonite is named for Red Canyon in southeast Utah, USA.