Clark and others 2007 USGS Data Series 231
Spectral Library splib06a Sample Description

(For further information on spectroscopy, see: http://speclab.cr.usgs.gov)

TITLE: Alunite0.66K+.34Na CU91-217A DESCRIPT

DOCUMENTATION_FORMAT: MIXTURE

SAMPLE_ID: CU91-217A

MIXTURE_TYPE: Intimate

MIXTURE: Alunite 66% 0.00XNa + 34% 0.83XNa

FORMULA: (K)Al3(SO4)2(OH)6 + (Na.83,K.17)Al3(SO4)2(OH)6

FORMULA_HTML: KAl₃(SO₄)₂(OH)₆ + (Na_0.83,K_0.17)Al₃(SO₄)₂(OH)₆

COLLECTION_LOCALITY: Cuprite, Nevada USA

ORIGINAL_DONOR: Gregg Swayze

COLLECTION_LATITUDE: Not Available # degrees and decimal minutes (N or S)

COLLECTION_LONGITUDE: Not Available # degrees and decimal minutes (W or E) P> DATUM: Not Available # 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, also quartz and well crystallized kaolinite (analysis by Steve Sutley on CU91-217A1)

END_XRD_ANALYSIS.

COMPOSITIONAL_ANALYSIS_TYPE: XRF # XRF, EM(WDS), ICP(Trace), WChem

COMPOSITION_TRACE: None

COMPOSITION_DISCUSSION:

XRF analysis indicated that the combined alunite's phases have a 0.176XNa composition. 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:

Finely crystallized alunite and quartz.

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. Kaolinite contaminants may form a band on the short wavelength side of the alunite bands. There is also a band at 1.769 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: 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:	splib05a r 7358	1.3-5.3µm	200	g.s.=
LIB_SPECTRA:	splib06a r 24051			g.s.=