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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: Limonite HS41 DESCRIPT

DOCUMENTATION_FORMAT: MINERAL

SAMPLE_ID: HS41

MINERAL_TYPE: Hydroxide

MINERAL: Limonite (mixture of hydrated lepidocrocite, goethite, and hematite)

FORMULA: FeO*OH*nH2O

FORMULA_HTML: FeO•OH•nH2O

COLLECTION_LOCALITY: Tuscaloosa County, Alabama

ORIGINAL_DONOR: Hunt and Salisbury Collection

CURRENT_SAMPLE_LOCATION: USGS Denver Spectroscopy Laboratory

ULTIMATE_SAMPLE_LOCATION: USGS Denver Spectroscopy Laboratory

SAMPLE_DESCRIPTION:

Original spectrum published in: Hunt, G.R., J.W. Salisbury, and C.J. Lenhoff, 1971, Visible and near-infrared spectra of minerals and rocks: III. Oxides and hydroxides. Modern Geology, v. 2, p. 195-205.

With the note:"Much limonite is actually cryptocrystalline goethite or lepidocrocite along with along with hematite, and additional water in some form. Colloidal silica, organic material, phosphates and clay minerals are also often present. Consequently, the name limonite is usually used as a field term for poorly characterized hydrated ferric oxide material. The water content of limonite is variable, but it typically contains 12% to 14% water by weight (Deer et al., 1962). This particular sample displays the change from opaque to transparent behavior near 0.55µm, and the band near 0.9µm typical of the ferric oxides. Because this sample is more transparent, these features are much more clearly resolved here. It also shows quite clearly the water of hydration bands near 1.4 and 1.9 µm for the larger particle size samples."

END_SAMPLE_DESCRIPTION.

XRD_ANALYSIS:

Goethite - major
Unidentifiable residual
No evidence of hematite

Konnert, Judith and Marta Flohr, 1992, unpublished data, USGS Reston, VA.

END_XRD_ANALYSIS.

COMPOSITIONAL_ANALYSIS_TYPE: None # XRF, EM(WDS), ICP(Trace), WChem
COMPOSITION_TRACE:

COMPOSITION_DISCUSSION:

None.

END_COMPOSITION_DISCUSSION.

MICROSCOPIC_EXAMINATION:

END_MICROSCOPIC_EXAMINATION.

SPECTROSCOPIC_DISCUSSION:

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: splib04a r 2788 0.2-3.0µm 200 g.s.=
LIB_SPECTRA: splib05a r 4169 0.2-3.0µm 200 g.s.=


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