Travis Olds
Susan Hall
Bradley S. Van Gosen
Anthony Kampf
Peter Burns
Joe Marty
Tyler P. Spear
2023
<div class=""><div id="135597287" class="article-section-wrapper js-article-section js-content-section " data-section-parent-id="0"><p>Finchite (IMA2017-052), Sr(UO<sub>2</sub>)<sub>2</sub>(V<sub>2</sub>O<sub>8</sub>)·5H<sub>2</sub>O, is the first uranium mineral known to contain essential Sr. The new mineral occurs as yellow-green blades up to ~10 µm in length in surface outcrops of the calcrete-type uranium deposit at Sulfur Springs Draw, Martin County, Texas, U.S.A. Crystals of finchite were subsequently discovered underground in the Pandora mine, La Sal, San Juan County, Utah, U.S.A., as diamond-shaped golden-yellow crystals reaching up to 1 mm. The crystal structure of finchite from both localities was determined using single-crystal X-ray diffraction and is orthorhombic,<span> </span><i>Pcan,</i><span> </span>with<span> </span><i>a</i><span> </span>= 10.363(6) Å,<span> </span><i>b</i><span> </span>= 8.498(5) Å,<span> </span><i>c</i><span> </span>= 16.250(9) Å,<span> </span><i>V</i><span> </span>= 1431.0(13) Å<sup>3</sup>,<span> </span><i>Z</i><span> </span>= 4 (R<sub>1</sub><span> </span>= 0.0555) from Sulfur Springs Draw; and<span> </span><i>a</i><span> </span>= 10.3898(16),<span> </span><i>b</i><span> </span>= 8.5326(14),<span> </span><i>c</i><span> </span>= 16.3765(3) Å,<span> </span><i>V</i><span> </span>= 1451.8(4) Å<sup>3</sup>,<span> </span><i>Z</i><span> </span>= 4 (R<sub>1</sub><span> </span>= 0.0600) from the Pandora mine. Electron-probe microanalysis provided the empirical formula (Sr<sub>0.88</sub>K<sub>0.17</sub>Ca<sub>0.10</sub>Mg<sub>0.07</sub>Al<sub>0.03</sub>Fe<sub>0.02</sub>)<sub>Σ1.20</sub>(UO<sub>2</sub>)<sub>2</sub>(V<sub>2.08</sub>O<sub>8</sub>)·5H<sub>2</sub>O for crystals from Sulfur Springs Draw, and (Sr<sub>0.50</sub>Ca<sub>0.28</sub>Ba<sub>0.22</sub>K<sub>0.05</sub>)<sub>Σ0.94</sub>(U<sub>0.99</sub>O<sub>2</sub>)<sub>2</sub>(V<sub>2.01</sub>O<sub>8</sub>)·5H<sub>2</sub>O for crystals from the Pandora mine, based on 17 O atoms per formula unit. The structure of finchite contains uranyl vanadate sheets based upon the francevillite topology. Finchite is a possible immobilization species for both uranium and the dangerous radionuclide<span> </span><sup>90</sup>Sr because of the relative insolubility of uranyl vanadate minerals in water.</p></div></div>
application/pdf
10.2138/am-2022-8365
en
Mineralogical Society of America
Finchite, Sr(UO2)2(V2O8)·5H2O, a new uranyl sorovanadate with the francevillite anion topology
article