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: Alunite0.35K+.65Na CU91-217H DESCRIPT

DOCUMENTATION_FORMAT: MIXTURE

SAMPLE_ID: CU91-217H

MIXTURE_TYPE: Intimate

MIXTURE: Alunite 35% 0.00XNa + 65% 0.74XNa

FORMULA: (K)Al3(SO4)2(OH)6 + (Na.74,K.26)Al3(SO4)2(OH)6

FORMULA_HTML: KAl₃(SO₄)₂(OH)₆ + (Na_0.74,K_0.26)Al₃(SO₄)₂(OH)₆

COLLECTION_LOCALITY: Cuprite, Nevada USA

ORIGINAL_DONOR: Gregg Swayze

COLLECTION_LATITUDE: N37deg 31.433' # degrees and decimal minutes (N or S)

COLLECTION_LONGITUDE: W117deg 12.683' # degrees and decimal minutes (W or E)

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 contains two alunite phases from the western side of Alunite Hill in the western hydrothermal center at Cuprite. It was deposited by hot hydrothermal fluids that altered lower Cambrian Harkless Phyllite about 7 m.y. ago.

END_SAMPLE_DESCRIPTION.

XRD_ANALYSIS:

Natroalunite, quartz (analysis by Steve Sutley on CU91-217H1)

END_XRD_ANALYSIS.

COMPOSITIONAL_ANALYSIS_TYPE: None # XRF, EPMA, ICP(Trace), WChem

COMPOSITION_TRACE: None

COMPOSITION_DISCUSSION:

Bulk compositional analysis indicates sample is XNa = 0.64 (treats sample as if it is a single alunite phase). Composition of each alunite phase was estimated using the position of the 3.85 micron D-O stretch bands according to the calibration in Swayze (1997).

END_COMPOSITION_DISCUSSION.

MICROSCOPIC_EXAMINATION:

Fine-grained and coarse-grained alunite plus quartz. Coarse alunite may have formed along veins.

END_MICROSCOPIC_EXAMINATION.

SPECTROSCOPIC_DISCUSSION:

The spectrum is dominated by strong OH stretch overtone absorptions in the 1.45 micron region with two main bands. In this case because of the two alunite phase there are four OH stretch bands. There is also a band at 1.767 microns characteristic of alunite. The main alunite absorption complex near 2.17 microns may be due to a SO3-O...H-O stretch/bend combination band. There is also a band around 2.32 microns. This band and the others vary in position as a function of Na and K content and the depth of the bands may vary as a function of formation temperature (Swayze, 1997).

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: 1b2b3_4_ # 1= 0.2-3, 2= 1.5-6, 3= 6-25, 4= 20-150 microns