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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.
IMAGE_OF_SAMPLE:
NO PHOTO
END_SAMPLE_DESCRIPTION.
XRD_ANALYSIS:
Not Available
END_XRD_ANALYSIS.
COMPOSITIONAL_ANALYSIS_TYPE: # XRF, EPMA, 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