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A Natural Vanadate–Arsenate Isomorphous Series with Jeffbenite-Type Structure: New Fumarolic Minerals Udinaite, NaMg 4 (VO 4) 3 , and Arsenudinaite, NaMg 4 (AsO 4) 3.
- Source :
- Minerals (2075-163X); Jul2022, Vol. 12 Issue 7, pN.PAG-N.PAG, 16p
- Publication Year :
- 2022
-
Abstract
- Two new isostructural minerals udinaite and arsenudinaite with the end-member formulae NaMg<subscript>4</subscript>(VO<subscript>4</subscript>)<subscript>3</subscript> and NaMg<subscript>4</subscript>(AsO<subscript>4</subscript>)<subscript>3</subscript>, respectively, are found in the Arsenatnaya fumarole, Tolbachik volcano, Kamchatka, Russia. They are associated with one another and anhydrite, diopside, hematite, schäferite, berzeliite, svabite, calciojohillerite, tilasite, reznitskyite, ludwigite, rhabdoborite-group borates, forsterite, magnesioferrite, fluorapatite, pliniusite, and powellite. Both minerals occur as equant tetragonal prismatic–dipyramidal crystals up to 0.15 mm, aggregates up to 1 cm and interrupted crusts up to 2 × 2 cm<superscript>2</superscript>. Udinaite and arsenudinaite, visually indistinguishable from one another, are transparent, beige or brownish-yellowish, with vitreous lustre. Both minerals are optically uniaxial (–); ω = 1.785/1.777 and ε = 1.830/1.820, D<subscript>calc.</subscript> = 3.613/3.816 g·cm<superscript>−3</superscript> (udinaite/arsenudinaite). The empirical formulae are: udinaite: (Na<subscript>0.55</subscript>Ca<subscript>0.16</subscript>)<subscript>Σ0.71</subscript>(Mg<subscript>4.04</subscript>Mn<subscript>0.02</subscript>Fe<subscript>0.01</subscript>)<subscript>Σ4.07</subscript>(V<subscript>1.63</subscript>As<subscript>1.05</subscript>P<subscript>0.28</subscript>Si<subscript>0.03</subscript>S<subscript>0.01</subscript>)<subscript>Σ3.00</subscript>O<subscript>12</subscript>; arsenudinaite: (Na<subscript>0.57</subscript>Ca<subscript>0.13</subscript>)<subscript>Σ0.70</subscript>(Mg<subscript>4.01</subscript>Mn<subscript>0.01</subscript>Fe<subscript>0.01</subscript>)<subscript>Σ4.03</subscript>(As<subscript>2.07</subscript>V<subscript>0.84</subscript>P<subscript>0.10</subscript>Si<subscript>0.01</subscript>S<subscript>0.01</subscript>)<subscript>Σ3.03</subscript>O<subscript>12</subscript>. Both minerals are tetragonal, I-42d, Z = 4, a = 6.8011(2)/6.8022(1), c = 19.1839(12)/19.1843(6) Å, and V = 887.35(7)/887.66(4) Å<superscript>3</superscript>, R<subscript>1</subscript> = 0.0287/0.0119 (udinaite/arsenudinaite). Their crystal structure consists of the helical chains of edge-sharing MgO<subscript>6</subscript> octahedra and isolated TO<subscript>4</subscript> tetrahedra, forming a heteropolyhedral pseudo-framework with Na cations located in cavities. Both minerals are isostructural to jeffbenite. Udinaite and arsenudinaite form an isomorphous series in which the contents of T constituents vary within (in apfu): V<subscript>1.6–0.1</subscript>As<subscript>2.8–1.0</subscript>P<subscript>0.4–0.0</subscript>. [ABSTRACT FROM AUTHOR]
- Subjects :
- MINERALS
FLUORAPATITE
CRYSTAL structure
HELICAL structure
TETRAHEDRA
DIOPSIDE
Subjects
Details
- Language :
- English
- ISSN :
- 2075163X
- Volume :
- 12
- Issue :
- 7
- Database :
- Complementary Index
- Journal :
- Minerals (2075-163X)
- Publication Type :
- Academic Journal
- Accession number :
- 158299309
- Full Text :
- https://doi.org/10.3390/min12070850