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: Opalized Tuff CU00-15E DESCRIPT

DOCUMENTATION_FORMAT: MIXTURE

SAMPLE_ID: CU00-15E

MIXTURE_TYPE: Intimate

MIXTURE: Opal + others

FORMULA: SiO2*nH2O + others

FORMULA_HTML: SiO₂*nH₂O + others

COLLECTION_LOCALITY: Opal Hill, Eastern Alteration Center, Cuprite, Nevada, USA

ORIGINAL_DONOR: Gregg Swayze

COLLECTION_LATITUDE: N37 32.83' # degrees and decimal minutes (N or S)

COLLECTION_LONGITUDE: W117 10.02' # 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 freshly exposed silica quarry on Opal Hill in the central portion of the eastern alteration center along its eastern margin. The sample was collected from an altered Tertiary Tuff that underwent hydrothermal alteration about 6.6 Ma.

END_SAMPLE_DESCRIPTION.

XRD_ANALYSIS:

Cristobalite and/or opal (major), quartz (major), calcite (minor), tridymite (trace).

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 absorptions characteristic of opal. In particular is the small shoulder at 1.4602 microns on the long wavelength side of the 1st OH stretch overtone at 1.4087 microns. This should appear in samples bearing cristobalite or opal. There is also a broad Si-OH combination band at 2.2165 microns that is a bit narrower than in chalcedony (e.g. compare with CU91-6A).

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history of the Cuprite Mining District, southwestern Nevada: an integrated geological and geophysical approach: unpublished Ph.D. Dissertation, University of Colorado at Boulder, 399p.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