Metamunirite, a New Anhydrous Sodium Metavanadate from San Miguel County, Colorado

Howard T. Evans Jr.
U.S. Geological Survey, Reston, Virginia 22092, U.S.A.

Abstract: Metamunirite, β-NaVO3, is found in cavities in sandstone in San Miguel County, Colorado, occurring as fine, fibrous, colourless needles. X-ray powder and precession photographs show the crystals to be orthorhombic, space group Pnma, with a = 14.134(7), b = 3.648(2), c = 5.357(2) Å. They are optically biaxial positive with nα = 1.780(2) (‖c), nβ = 1.800(2) (‖a), nγ ≫ 185 (‖b, fibre axis; positive elongation), 2Vz moderate. A crystal structure analysis, confirming the previously determined structure of β-NaVO3, shows the presence of (VO3)n chains made up of zig-zag VO5 square pyramids. Metamunirite is probably formed by dehydration of munirite, NaVO3.2H2O.

Keywords: metamunirite • vanadates • San Miguel County, Colorado • munirite

Mineralogical Magazine; December 1991 v. 55; no. 381; p. 509-513; DOI: 10.1180/minmag.1991.055.381.02
© 1991, The Mineralogical Society
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