(For further information on spectrsocopy, see:
TITLE: Stonewall Playa Dry Mud Field DESCRIPT
MIXTURE: all components of dry playa mud
FORMULA: Not Available
FORMULA_HTML: Not Available
COLLECTION_LOCALITY: Stonewall Playa, Cuprite, Nevada USA
ORIGINAL_DONOR: Gregg Swayze
COLLECTION_LATITUDE: Square Corners: N37 32.05', N37 32.067', N37 32.0167', N37 32.0167' # degrees and decimal minutes
COLLECTION_LONGITUDE: Square Corners: W117 09.367', W117 09.333', W117 09.35', W117 09.383' #degrees and decimal minutes
DATUM: NAD27 # coordinate datum
CURRENT_SAMPLE_LOCATION: Not a sample
ULTIMATE_SAMPLE_LOCATION: Not a sample
This is not a spectrum of a collected sample but it is an average of 174 spectra collected of the Stonewall Playa surface when it was dry on Aug. 28th, 2001. The field spectra where collected in a polygonal area denoted by the GPS coordinates corners given above. Spectra were collected while holding the spectrometer fiber optic about 1 meter above the surface and walking while collecting. This proceedure smears the spectrum collection over an oval area a couple of meters long. About 6 offset traverses were made in each of two orthogonal direction within the sample polygon. This polygon is located a couple of hundred meters northeast of the big engraved "peace" sign. All 174 spectra were averaged, then corrected to absolute reflectance using a National Institue of Standards spectralon correction. Atmospheric absorptions were minimal during spectral collection and were removed from the averaged spectrum by physically moving the spectrum data points one at a time into positions corresponding to the ground reflectance given by laboratory spectra of a series of field samples. Only data points near 1.2, 1.4, 1.9, and 2.05 microns were modified in this way to remove all traces of atmospheric residues in the field spectra. The sample polygon is approximately a few hundred meters on a side.
Quartz (major), anorthite (minor), albite (minor), calcite (minor), orthoclase (minor), muscovite (minor), montmorillonite (minor), kaolinite (trace), magnesiohornblende (trace). XRD information from field sample Na-Montmorillonite CU93-52A collected 300 meters to the south of the field spectrum polygon.
COMPOSITIONAL_ANALYSIS_TYPE: XRF # XRF, EM(WDS), ICP(Trace), WChem
The spectrum is relatively bright with an over all reflectance of about 54%. Spectral absorptions are weak with the strongest 1.908 microns due to adsorbed or structural water in hydrated phases. The 1st OH overtone is located at 1.4110 microns. There is a weak Fe-absorption at 0.9127 microns. The 6% band at 2.2074 microns is mostly due to montmorillonite with contributions from muscovite. A very weak calcite band may be indicated by a .3% absorption at 2.344 microns.
SPECTRAL_PURITY: 1a2_3_4_ # 1= 0.2-3, 2= 1.5-6, 3= 6-25, 4= 20-150 microns
|LIB_SPECTRA:||splib05a r 8996||0.2-3.0µm||200||g.s.=|
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