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(For further information on spectroscopy, see:
http://speclab.cr.usgs.gov)
TITLE: Goethite WS219 (Limonite) DESCRIPT
DOCUMENTATION_FORMAT: MINERAL
SAMPLE_ID: WS219
MINERAL_TYPE: Hydroxide
MINERAL: Goethite
FORMULA: alpha-FeO(OH)
FORMULA_HTML: alpha-FeO(OH)
COLLECTION_LOCALITY: Tuscaloosa, Alabama
ORIGINAL_DONOR: Wards Natural Science Inc.
CURRENT_SAMPLE_LOCATION: USGS Denver Spectroscopy Laboratory
ULTIMATE_SAMPLE_LOCATION: USGS Denver Spectroscopy Laboratory
SAMPLE_DESCRIPTION:
Polymorphous with Akaganeite, Feroxyhyte, and Lepidocrocite.
IMAGE_OF_SAMPLE:
NO PHOTO
END_SAMPLE_DESCRIPTION.
XRD_ANALYSIS:
Not Available
END_XRD_ANALYSIS.
COMPOSITIONAL_ANALYSIS_TYPE: None # XRF, EM(WDS), ICP(Trace), WChem
COMPOSITION_TRACE: None
COMPOSITION_DISCUSSION:
None.
END_COMPOSITION_DISCUSSION.
MICROSCOPIC_EXAMINATION:
mode:
50 vol% limonite coated quartz grains
35 vol% limonite small grains & limonite coated quartz
15 vol% limonite large grains
bimodal grain size distribution:
mode 1: average grain size limonite coating = 8 µm 30 vol%
mode 2: average grain size limonite grains = 60 µm 15 vol%
average grain size= 35 µm of limonite
Smaller limonite grains 80% coat larger limonite and quartz grains. Grains size too small or grains isotropic so I cannot determine optical properties. In plain light grains resemble plates and not fibres suggesting the possible dominance of lepidochrocite? Yellow-brown color and high relief. G. Swayze.
END_MICROSCOPIC_EXAMINATION.
SPECTROSCOPIC_DISCUSSION:
END_SPECTROSCOPIC_DISCUSSION.
SPECTRAL_PURITY: 1c2_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: | splib04a r 1802 | 0.2-3.0µm | 200 | g.s.= 35 µm |
| LIB_SPECTRA: | splib05a r 2879 | 0.2-3.0µm | 200 | g.s.= |
| LIB_SPECTRA: | splib06a r 8380 | g.s.= |