Orthominasragrite, V4+O (SOb>4b>) (Hb>2b>O)b>5b>, is a new mineral species from Temple Mountain, Emery County, Utah. It occurs as rounded aggregates (up to ~200 μm across) of irregular grains that are pale blue to bright blue, depending on size. Orthominasragrite has a pale blue streak, a vitreous luster, and no observable fluorescence under ultraviolet light. It has no cleavage or parting. The Mohs hardness is ~1, and the calculated density is 2.00 g/cm3. Orthominasragrite is biaxial negative (pseudo-uniaxial) with α 1.529(2), β 1.534(2), γ 1.534(2), 2Vb>obsb> = 2(4)°, 2Vb>calcb> = 0°, non-pleochroic, X = b, Y = c, Z = a. Orthominasragrite is orthorhombic, space group Pmn2b>1b>, a 7.246(4), b 9.333(6), c 6.210(4) Å, V 420.0(3) Å3, Z = 2. The strongest seven lines in the X-ray powder-diffraction pattern [d in Å(I)(hkl)] are as follows: 4.699(10)(101,020), 3.322(5)(121), 2.865(4)(220), 2.602(3)(221,131,022), 3.734(2)(021), 3.622(2)(200), and 3.108(2)(002). Chemical analysis by electron microprobe gave VOb>2b> 33.88, SOb>3b> 31.97, Hb>2b>O (calc.) 36.30, sum 102.15 wt.%; the proportion of Hb>2b>O was determined by crystal-structure analysis. The resulting empirical formula on the basis of 10 anions (including 5 Hb>2b>O) is Vb>1.014b> Sb>0.991b> Ob>5b> (Hb>2b>O)b>5b>; the end-member formula is VO (SOb>4b>) (Hb>2b>O)b>5b>. Orthominasragrite is the orthorhombic form of (monoclinic) minasragrite. The crystal structure was solved by direct methods and refined to an R index of 4.4% for 1007 observed (|Fb>ob>| > 5σF) reflections measured with an automated four-circle X-ray diffractometer using MoKα X-radiation. There is one V site occupied by V4+ and surrounded by one O atom and 5 (Hb>2b>O) groups in an octahedral arrangement, with one short apical vanadyl bond (1.580 Å), four similar equatorial bonds (<2.026 Å>), and one longer V–O bond (2.231 Å) trans to the vanadyl bond. The structure consists of isolated (V4+ϕb>6b>) octahedra (ϕ: unspecified anion) and (SOb>4b>) tetrahedra linked by hydrogen bonds.
