Quick
Search: 		  
advanced search
 GSW Home   GeoRef Home   My GSW Alerts   Contact GSW   About GSW   Journals List   Help 
American Mineralogist Email Content Delivery
JOURNAL HOME HELP CONTACT PUBLISHER SUBSCRIBE ARCHIVE SEARCH TABLE OF CONTENTS
American Mineralogist; February 1998; v. 83; no. 1-2; p. 172-177
This Article
Right arrow Full Text (PDF)
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Services
Right arrow Email this article to a friend
Right arrow Similar articles in this journal
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Citing Articles
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Birch, W. D.
Right arrow Articles by McCammon, C. A.
Right arrow Search for Related Content
GeoRef
Right arrow GeoRef Citation

Bamfordite, Fe (super 3+) Mo 2 O 6 (OH) 3 .H 2 O, a new hydrated iron molybdenum oxyhydroxide from Queensland, Australia; description and crystal chemistry

William D. Birch, Allan Pring, E. Maude McBriar, Bryan M. Gatehouse, and Catherine A. McCammon

Museum of Victoria, Department of Mineralogy, Melbourne, Vic., Australia

Bamfordite from the abandoned W-Mo-Bi mines at Bamford, Queensland, Australia, is a new hydrated iron molybdate with a unique structure. This mineral formed by oxidation of molybdenite, MoS 2 . in the presence of strongly acidic solutions. It occurs as microcrystalline aggregates of tabular triclinic crystals between 0.005 and 0.05 mm long. The aggregates are apple-green with an earthy luster and greenish yellow streak. Crystals are transparent, with pale to moderate yellow-green pleochroism. They show principal forms {001}, {100}, {010}, {110}, {110}, and prominent (100) cleavage traces. The Mohs hardness is 2-3 and the measured density is 3.620 g/cm 3 (calculated density is 3.616 g/cm 3 ). Crystals are biaxial negative and length slow, with RIs of alpha = 1.91, beta = 2.03, and gamma = 2.11, and 2V nearly equal 90 degrees . Chemical analysis yielded an empirical formula of Fe (super 3+) (sub 1.00) Mo (sub 2.01) W (sub 0.03) P (sub 0.02) O 10 H (sub 4.62) , calculated on the basis of ten O atoms. The simplified formula is Fe (super 3+) Mo 2 O 6 (OH) 3 .H 2 O, chosen on the basis of crystal-structure determination and Mossbauer spectroscopy results. Unit-cell parameters calculated both from the X-ray powder and single-crystal diffraction data are a = 5.889(5), b = 7.545(5), c = 9.419(5) Aa; alpha = 71.46(4) degrees , beta = 83.42(4) degrees ; gamma = 72.78(4) degrees ; V = 378.9(4) Aa 3 ; Z = 2; P1 or P1. The crystal structure was solved in P1 using direct methods and Fourier techniques. The final refinement based on 1486 observed reflections [I>2.00 sigma I] converged to R = 0.05 and R w = 0.038. The bamfordite crystal structure contains groups of four MoO 6 octahedra, linked by edge-sharing, which in turn are linked through corner-sharing to pairs of FeO 6 octahedra thereby forming infinite sheets parallel to (100). These sheets are stepped and linked by hydrogen bonding. No other molybdenum oxides have this or a similar structure, instead molybdates such as wulfenite, PbMoO 4 , are based on tetrahedrally coordinated molybdenum.

This record provided courtesy of AGI/GeoRef.






JOURNAL HOME HELP CONTACT PUBLISHER SUBSCRIBE ARCHIVE SEARCH TABLE OF CONTENTS
Copyright © 2009 by Mineralogical Society of America