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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: 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.

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 lepidochrosite? 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.=


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