ANORTHOMINASRAGRITE, V4+ O (SO4) (H2O)5, A NEW MINERAL SPECIES FROM TEMPLE MOUNTAI

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• journal_title：The Canadian Mineralogist
• Contributor：Mark A. Cooper ; Frank C. Hawthorne ; Joel D. Grice ; Patrick Haynes
• Publisher：Mineralogical Association of Canada
• Date：2003-
• Format：text/html
• Language：en
• Identifier：10.2113/gscanmin.41.4.959
• journal_abbrev：Can Mineral
• issn：0008-4476
• volume：41
• issue：4
• firstpage：959
• section：Articles

摘要

<p id="p-1">Anorthominasragrite, Vp>4+p> O (SO₄) (H₂O)₅, is a new mineral species from Temple Mountain, Emery County, Utah, U.S.A. It occurs as blue-green crusts and spherical granular aggregates (up to ~1 mm across) in a fossil (Triassic) tree; individual crystals are <0.1 mm and are intimately intergrown. Anorthominasragrite has a white 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 2.12 g/cmp>3p>. Anorthominasragrite is biaxial positive, with α 1.548, β 1.555, γ 1.574, all ±0.002, 2m>Vm>(obs.) = 86(1)°, 2m>Vm>(calc.) = 63°, non-pleochroic, m>Xm> ∧ m>cm> ≈ 18° (in β obtuse), m>Ym> ≈ m>a, Zm> ∧ m>bm> ≈ 19° (in γ obtuse). Anorthominasragrite is triclinic, space group m>Pm>1̅, m>am> 7.548(3), m>bm> 7.805(2), m>cm> 7.821(3) Å, α 79.03(4), β 71.94(3), γ 65.31(3)°, m>Vm> 397.1(2) Åp>3p>, m>Zm> = 2. The strongest seven lines in the X-ray powder-diffraction pattern [m>dm> in Å(m>Im>)(m>hklm>)] are: 6.617(100)(100), 7.053(80)(010), 4.116(80)(1̅10), 3.712(80)(121,002,211), 3.206(70)(221), 2.934(50)(11̅2, 1̅02), 5.314(30)(011). Chemical analysis with an electron microprobe gave VO₂ 33.93, SO₃ 30.78, H₂O (calc.) 35.52, sum 100.23 wt.%; the amount of H₂O was determined by crystal-structure analysis. The resulting empirical formula on the basis of 10 anions (including 5 H₂O) is V_1.04 S_0.98 O₅ (H₂O)₅; the end-member formula is V O (SO₄) (H₂O)₅. Anorthominasragrite is the triclinic polymorph of V O (SO₄) (H₂O)₅. The crystal structure of anorthominasragrite was solved by direct methods and refined to an m>Rm> index of 3.2% for 673 observed (|m>Fm>_o| > 5σm>Fm>) reflections measured with an automated four-circle X-ray diffractometer using Mom>Km>α X-radiation. There is one m>Vm> site occupied by Vp>4+p> and surrounded by three O atoms and three (H₂O) groups in an octahedral arrangement, with one short vanadyl bond (1.587 Å), four similar equatorial bonds (<2.013 Å>), and one longer V–O bond (2.253 Å) m>transm> to the vanadyl bond. The structure consists of (Vp>4+p>ϕ₆) (ϕ: unspecified anion) octahedra and (SO₄) tetrahedra that corner-share Op>2−p> vertices to form (Vp>4+p> O)₂ (H₂O)₆ (SO₄)₂ groups [as in bobjonesite, Vp>4+p> O (SO₄) (H₂O)₃], with two additional isolated (H₂O) groups. p>