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USGS Spectral Library Version 7 Sample Description

Kokaly, R.F., Clark, R.N., Swayze, G.A., Livo, K.E., Hoefen, T.M., Pearson, N.C., Wise, R.A., Benzel, W.M., Lowers, H.A., Driscoll, R.L., and Klein, A.J., 2017, USGS Spectral Library Version 7: U.S. Geological Survey Data Series 1035, 61 p., https://doi.org/10.3133/ds1035
For more information on the library, see: local link web link

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, EPMA, 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