U.S. DEPARTMENT OF THE INTERIOR 
U.S. GEOLOGICAL SURVEY

Open-File Report OFR 02-392: This report is available as a pdf file. 
 It can be can be opened and read using Adobe Reader. 
 A free copy of Adobe Reader 5.0 can be downloaded at
 http://www.adobe.com/products/acrobat/readstep.html.  
The web-ready pdf file was prepared by John Wallis.
 Dave Frank and Carolyn Donlin also contributed to completion
 of this on-line version of the report.

TITLE:   "MINERALOGICAL CHARACTERIZATION OF WEATHERED AND LESS WEATHERED
 STRATA OF THE MEADE PEAK PHOSPHATIC SHALE MEMBER OF THE PERMIAN PHOSPHORIA
 FORMATION Measured Sections E and F, Rasmussen Ridge, and Measured Sections
 G and H, Sage Creek area of the Webster Range, Caribou County, Idaho"
 by Andrew C. Knudsen, Mickey E. Gunter, James R. Herring, and
 Richard I. Grauch, Western U.S. Phosphate Project, 2002.

This 36-page report contains a narrative with four sets of figures and two
 sets of tables. This study uses powder X-ray diffraction (XRD) with Rietveld
 quantification software to characterize the mineralogy of channel samples
 from stratigraphic sections measured by the U.S. Geological Survey in the
 Meade Peak Phosphatic Shale Member of the Permian Phosphoria Formation. 
 Measured sections are at the Rasmussen Ridge mine and at the Smoky Canyon
 mine approximately 15 and 25 miles, respectively, northeast of Soda Springs,
 Idaho.  The dominant minerals present in these samples are
 carbonate-fluorapatite, which is the most common phosphatic ore mineral in
 this and other marine phosphorites, quartz, muscovite, albite, orthoclase,
 the ammonium feldspar buddingtonite (NH4AlSi3O8), dolomite, and calcite. 
 Because of their potential for hosting trace elements such as Se, the
 presence of minor pyrite and sphalerite is also noteworthy.  Analysis of
 the carbonate content in the carbonate-fluorapatite by Rietveld refinement
 shows relatively low carbonate contents, generally between 2 – 3% (wt.)
 CO32- in the apatite structure, compared to other marine phosphorites.  

The report is preliminary and has not been reviewed for conformity with U.S.
 Geological Survey editorial standards or with the North American
 Stratigraphic Code.  Any use of trade, product, or firm names is for
 descriptive purposes only and does not imply endorsement by the U.S. Government.

ACKNOWLEDGEMENTS:  The authors appreciate the help and participation of the
 Bureau of Land Management, the Forest Service, and staff at the
 Rasmussen Ridge (Agrium) and Smoky Canyon (J.R. Simplot) mines.