Mineral Resources Program

Figure 1 from USGS Fact Sheet 2019-3007 The Earth Mapping Resources Initiative (Earth MRI): Mapping the Nation’s Critical Mineral Resources.

Figure 1. Planned applications for data acquired during the Earth Mapping Resources Initiative (Earth MRI). Images are from the U.S. Geological Survey (USGS). Sources for images in left column, from top to bottom: Topography:

Table 6.  Summary of OH-related near-infrared spectral features of unexpanded and expanded vermiculite ores.

Notes: Vibrational positions from spectra of handpicked, ground mica flakes from the unexpanded GDS469 ore sample from Libby, MT; and the expanded vermiculite ores as noted.  Vibrational assignments from this study.  o_a = OH overtone;

Table 7.  Accuracy of expanded vermiculite ore spectral source determinations and impurity detections. 

Notes: Samples evaluated for impurities using the Modified Cincinnati Method (MCM) with separates examined by Scanning Electron Microscope – Energy-Dispersive X-Ray Spectroscopy (SEM-EDS) for the presence of amphibole, talc, and/or serpentine, and using the

Table A1.  ANOVA with post hoc multiple pairwise statistical comparison between compositions of unexpanded vermiculite ore samples examined in this study.

Notes: Mg fraction = Mg/(Mg+Al^oct +Fe^oct), tetrahedral Al fraction = (Al^tet + Si), total Al, and total Fe are based on Electron Probe MicroAnalysis (EPMA) of the

Table A2.  ANOVA with post hoc multiple pairwise statistical comparison between compositions of expanded vermiculite ore samples examined in this study. 

Notes: Mg fraction = Mg/(Mg+Al^oct +Fe^oct), tetrahedral Al fraction = (Al^tet + Si), total Al, and total Fe are based on Electron Probe MicroAnalysis (EPMA) of the expanded ore

Table A3.  ANOVA with post hoc multiple pairwise statistical comparison between compositions of the selected unexpanded vermiculite ore samples and all other unexpanded vermiculite ore samples from the four major historical sources examined in this study.

Notes: Mg fraction = Mg/(Mg+Al^oct +Fe^oct), tetrahedral Al fraction = (Al^tet +

Table A4.  ANOVA with post hoc multiple pairwise statistical comparison between compositions of selected unexpanded vermiculite ore samples examined in this study. 

Notes: Mg fraction = Mg/(Mg+Al^oct +Fe^oct), tetrahedral Al fraction = (Al^tet + Si),  total Al, and total Fe are based on Electron Probe MicroAnalysis (EPMA) of the

Table A5.  Electron probe microanalysis analyses and resulting formula of an unexpanded VTx-1 Mg-vermiculite sample from Llano, Texas. 

Notes:

^a Microprobe data for all Fe are binned into FeO.

^b There are no data on H₂O content. 

Table 1.  Expanded vermiculite ores examined in this study: their sources and amphibole, talc, and/or serpentine impurities.

Notes: XRD = X-ray diffraction analysis of bulk ore samples (B) and sink fractions (S).  SEM-EDS = Scanning Electron Microscope – Energy-Dispersive X-Ray Spectroscopy.  Band Depth Ratio = 1.40/1.42-µm band depth ratio.  The use of "sodic-

Table 2.   Average EPMA chemical analyses and calculated mineral formulas of selected unexpanded vermiculite ores.

Notes: Compositions of bulk samples not individual minerals.  n = number of microprobe spot analyses collected on multiple mica flakes used to calculate the averaged composition of each sample.   ---- = not enough cation Al and/or Mg to assign to this

Table 3.  Mössbauer spectral parameters obtained at 295 K for selected unexpanded vermiculite ore samples.

Notes: IS = isomer shift; QS = quadrupole splitting; Width = absorption peak width; Area = % area of an absorption peak relative to other peaks in the spectrum.  

^a O_h1 & O_h2 = 1st and 2nd octahedral Fe³⁺