Sample Description USGS Spectral Library Version 7

USGS Spectral Library Version 7 Sample Description

Kokaly, R.F., Clark, R.N., Swayze, G.A., Livo, K.E., Hoefen, T.M., Pearson, N.C., Wise, R.A., Benzel, W.M., Lowers, H.A., Driscoll, R.L., and Klein, A.J., 2017, USGS Spectral Library Version 7: U.S. Geological Survey Data Series 1035, 61 p., https://doi.org/10.3133/ds1035
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TITLE: Hematite_Thin_Film GDS27 DESCRIPT

DOCUMENTATION_FORMAT: MIXTURE

SAMPLE_ID: GDS27

MIXTURE_TYPE: Coating

MIXTURE: Hematite

FORMULA: alpha-Fe2O3

FORMULA_HTML: alpha-Fe₂O₃

COLLECTION_LOCALITY: Chemical Reagent purchased from vendor.

ORIGINAL_DONOR: sample prepared by Gregg Swayze

COLLECTION_LATITUDE: Not Available # degrees and decimal minutes (N or S)

COLLECTION_LONGITUDE: Not Available # degrees and decimal minutes (W or E)

DATUM: Not Available # coordinate datum

CURRENT_SAMPLE_LOCATION: USGS Denver Spectroscopy Laboratory

ULTIMATE_SAMPLE_LOCATION: USGS Denver Spectroscopy Laboratory

SAMPLE_DESCRIPTION:

Sample was prepared from a chemical reagent of Fe2O3. Fine grained powder was mixed with water and an eye-dropper was used to deposit a thin coating on a microscope glass thin section. The sample was dried over night and them measured spectrally. Our goal was to unsaturate the goethite bands and mimic the spectral absorptions found in natural goethite coatings.

END_SAMPLE_DESCRIPTION.

XRD_ANALYSIS:

Pure Hematite (See Hematite GDS27)

END_XRD_ANALYSIS.

COMPOSITIONAL_ANALYSIS_TYPE: None # XRF, EPMA, ICP(Trace), WChem

COMPOSITION_TRACE: None

COMPOSITION_DISCUSSION:

None

END_COMPOSITION_DISCUSSION.

MICROSCOPIC_EXAMINATION:

END_MICROSCOPIC_EXAMINATION.

For hematite powder:
average grain size = 200 microns (aggregates) Material opaque, but hematite red in powdered form. No impurities observed. Large 50-150 micron grain aggregates are composed of 2-3 micron grains. G. Swayze.

SPECTROSCOPIC_DISCUSSION:

Spectrum has Fe-related absorptions characteristic of hematite. Bands are located at 0.5427, 0.6615, and 0.8675 microns. Of note is the narrow width of the 0.8675 micron band: it is only 157 nm wide -- much narrower than in spectra of powdered hematite samples. Apparently the band narrows most on the long wavelength side of this band in coatings.

END_SPECTROSCOPIC_DISCUSSION.

SPECTRAL_PURITY: 1a2_3_4_ # 1= 0.2-3, 2= 1.5-6, 3= 6-25, 4= 20-150 microns