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Clark et. al. 2003 USGS Open File Report 03-395
Spectral Library splib05a Sample Description

(For further information on spectrsocopy, see: http://speclab.cr.usgs.gov)

TITLE: Geothite MPCMA2-C DESCRIPT

DOCUMENTATION_FORMAT: MINERAL

SAMPLE_ID: MPCMA2-C

MINERAL_TYPE: Hydroxide

MINERAL: Goethite

FORMULA: alpha-FeO(OH)

FORMULA_HTML: alpha-FeO(OH)

COLLECTION_LOCALITY: Coliseum mine area, Mountain Pass, California, USA

ORIGINAL_DONOR: Roger Clark

CURRENT_SAMPLE_LOCATION: U.S.G.S. Denver Spectroscopy Laboratory.

ULTIMATE_SAMPLE_LOCATION: U.S.G.S. Denver Spectroscopy Laboratory.

SAMPLE_DESCRIPTION:

Medium coarse grained rock coating. Visual estimate of grain size.

END_SAMPLE_DESCRIPTION.

XRD_ANALYSIS:

Not Available

END_XRD_ANALYSIS.

COMPOSITIONAL_ANALYSIS_TYPE: # XRF, EM(WDS), ICP(Trace),WChem

COMPOSITION_TRACE: None

COMPOSITION_DISCUSSION:

END_COMPOSITION_DISCUSSION.

MICROSCOPIC_EXAMINATION:

END_MICROSCOPIC_EXAMINATION.

SPECTROSCOPIC_DISCUSSION:

Spectral absorptions at 0.501, 0.666, and 0.954 microns are all characteristic of goethite. Bands around 1.4 and 2.2 microns are probably due to underlying muscovite in the host rock. A weak absorption at 2.65 microns may indicate the presence of jarosite but evidence of jarosite is lacking in the 1 micron region. It is possible that jarosite may underlie the goethite coating which is totally opaque at 1.0 micron but transparent past about 1.5 microns allowing photons to penetrate beneath the coating to the underlying jarosite.

END_SPECTROSCOPIC_DISCUSSION.

SPECTRAL_PURITY: 1b2_3_4_ # 1= 0.2-3, 2= 1.5-6, 3= 6-25, 4= 20-150 microns

LIB_SPECTRA_HED: where Wave Range Av_Rs_Pwr Comment
LIB_SPECTRA: splib05a r 2864 0.2-3.0µm 200 g.s.=


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