• journal_title：American Mineralogist
• Contributor：Joël Brugger ; Sergey V. Krivovichev ; Peter Berlepsch ; Nicolas Meisser ; Stefan Ansermet ; Thomas Armbruster
• Publisher：Mineralogical Society of America
• Date：2004-
• Format：text/html
• Language：en
• journal_abbrev：American Mineralogist
• issn：0003-004X
• volume：89
• issue：2-3
• firstpage：339
• section：Articles

Spriggite, Pb₃ [(UO₂)₆O₈(OH)₂](H₂O)₃, is a new hydrated Pb uranyl oxyhydroxide found near Arkaroola, Northern Flinders Ranges, South Australia. The new mineral’s name honors geologist and conservationist Reginald Claude Sprigg (1919–1994), founder of the Arkaroola Tourist Station. Together with beta-uranophane, soddyite, kasolite, Ce-rich francoisite-(Nd), metatorbernite, billietite, Ba-bearing boltwoodite, schoepite, metaschoepite, and weeksite, spriggite results from the supergene alteration of U-Nb-REE-bearing hydrothermal hematite breccia. Spriggite forms prismatic crystals up to about 150 μm in length and up to 40 μm across. It is transparent, bright orange in color with vitreous luster, biaxial, n_min = 1.807; n_max = 1.891 (Na_D, 22.5 °C), non-fluorescent, brittle with an uneven fracture. It has a pale orange streak, Mohs’ hardness ~4, good cleavage along (100) and D_calc = 7.64(6)g/cm³ . The empirical formula is (Pb_2.77Ca_0.06Ba_0.04)_∑2.87U₆O_19.9(OH)₂ ·3H₂O, and the simplified formula is Pb₃[(UO₂)₆O₈(OH)₂] (H₂O)₃. Spriggite is monoclinic, C2/c , a = 28.355(9), b = 11.990(4), c = 13.998(4) Å, β = 104.248(5); V = 4613(3) ų , Z = 8. The strongest eight lines in the powder X-ray diffraction pattern are [d in Å (I)(hkl)]: 6.92(60)(400), 6.02(30)(112̅;020), 3.46(80)(800), 3.10(100)(204;6̅04;3̅32;5̅32), 2̅.74(30)(4̅40), 2.01(30)(336̅), 1.918(60)(10.04̅;14.04̅;11. 3̅2;1̅3̅.31), 1.738(30)(53̅6;1̅1̅.36). The structure has been solved from a crystal twinned on (001) and refined to R1 = 9.7%. The structure is based upon the [(UO₂)₆O₈(OH)₂]⁶⁺ sheets of uranyl polyhedra of the β-U₃O₈ anion topology with Pb²⁺ cations and H₂O groups in the interlayer. Billietite and spriggite contain only hexavalent U in the uranyl sheets, whereas the similar sheets in β-U₃O₈ contain U⁵⁺ and U⁶⁺ , and those in ianthinite U⁴⁺ and U⁶⁺. Spriggite has the highest Pb: U ratio among the known hydrated Pb uranyl oxyhydroxide minerals.