DOCUMENTATION_FORMAT: MINERAL

SAMPLE_ID: WS220

MINERAL_TYPE: Hydroxide

MINERAL: Goethite

FORMULA: alpha-FeO(OH)

FORMULA_HTML: alpha-FeO(OH)

COLLECTION_LOCALITY: Kent, Connecticut

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:

40 kV - 30 mA, 7.3-9.5 keV
File: gotht220.mdi, *.out (smear mount on quartz plate)
Found: quartz, minor goethite

Comment: Superbly sharp quartz reflections of moderate overall intensity indicates excellent crystallinity. Very weak, broad goethite reflections indicate poor crystallinity and possible low abundance (compare with "pure" goethite, GDS-134). Amorphous material may be present.

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:
60 vol% quartz
20 vol% large goethite grains
20 vol% small goethite grains

Bimodal goethite grain size distribution:
mode 1: av gr sz = 50 µm @ 50 vol%
mode 2: av gr sz = 10 µm @ 50 vol%
av gr sz = 36 µm

quartz av gr sz = 75 µm

Significant quartz contamination, quartz is 50% coated by goethite. Large goethite grians are 50% coated with smaller goethite grains. High relief, non-fibrous, platey (lepidochrosite?). Slight red pleochroism. G. Swayze.

The high quartz content reduces the strength of the saturated UV-Vis absorption bands, otherwise spectrally pure. R. Clark

END_MICROSCOPIC_EXAMINATION.

SPECTROSCOPIC_DISCUSSION:

END_SPECTROSCOPIC_DISCUSSION.

SPECTRAL_PURITY: 1_2_3_4_

LIB_SPECTRA_HED: where Wave Range Av_Rs_Pwr Comment

LIB_SPECTRA: splib04a r 1813 0.2-3.0µm 200 g.s.= 36 µm

LIB_SPECTRA: splib05a r ____ 0.2-3.0µm 200 g.s.=

LIB_SPECTRA: splib06a r ____ 1.5-25µm 250 g.s.=