Sample Description USGS Spectral Library Version 7

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
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TITLE: Nontronite + others CU00-13A DESCRIPT

DOCUMENTATION_FORMAT: MIXTURE

SAMPLE_ID: CU00-13A

MIXTURE_TYPE: Intimate

MIXTURE: Nontronite + other mineral phases

FORMULA: Na0.3Fe3+2(Si,Al)4O10(OH)2*nH2O

FORMULA_HTML: Na_0.3Fe³⁺₂(Si,Al)₄O₁₀(OH)₂*nH₂O

COLLECTION_LOCALITY: 5 km north of western center, Cuprite, Nevada, USA

ORIGINAL_DONOR: Gregg Swayze

COLLECTION_LATITUDE: N37 35.87' # degrees and decimal minutes (N or S)

COLLECTION_LONGITUDE: W117 14.07' # degrees and decimal minutes (W or E) P> DATUM: NAD27 # coordinate datum

CURRENT_SAMPLE_LOCATION: U.S.G.S. Denver Spectroscopy Laboratory

ULTIMATE_SAMPLE_LOCATION: U.S.G.S. Denver Spectroscopy Laboratory

SAMPLE_DESCRIPTION:

This sample was collected from a weathered outcrop of the Tertiary rhyolitic Spearhead member of the Stonewall Flats Tuff about 5 km north of the western center at Cuprite, NV. Rocks at this site bordering a small drainage were weathering in an exfoliation pattern.

END_SAMPLE_DESCRIPTION.

XRD_ANALYSIS:

Clay separate contains smectite (major), kaolinite (trace), and mica (trace). XRD was unable to identify specific mineralogy of the smectite.

END_XRD_ANALYSIS.

COMPOSITIONAL_ANALYSIS_TYPE: XRF # XRF, EPMA, ICP(Trace), WChem

COMPOSITION_TRACE: None

COMPOSITION_DISCUSSION:

None

END_COMPOSITION_DISCUSSION.

MICROSCOPIC_EXAMINATION:

None

END_MICROSCOPIC_EXAMINATION.

SPECTROSCOPIC_DISCUSSION:

The spectrum has an absorption at 2.2907 microns characteristic of nontronite (e.g. Nontronite NG-1 has a similar band at 2.2883 microns). A weak absorption at 2.2408 microns may be from a ferrouginous smectite. A sharp narrow absorption at 0.4490 microns may be from nontronite but is at a slightly shorter wavelength than a similar band in Nontronite NG-1 (e.g. at 0.4600 microns). Alternatively this narrow band may be from an Fe-sulfide mineral.

See: Swayze, G.A., 1997, The hydrothermal and structural history of the Cuprite Mining District, southwestern Nevada: an integrated geological and geophysical approach: unpublished Ph.D. Dissertation, University of Colorado at Boulder, 399p.

END_SPECTROSCOPIC_DISCUSSION.

SPECTRAL_PURITY: 1b2_3_4_ # 1= 0.2-3, 2= 1.5-6, 3= 6-25, 4= 20-150 microns