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Clark et. al. 2003 USGS Open File Report 03-395
Spectral Library splib05a Sample Description

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

TITLE: Alunite SUSTDA-20 DESCRIPT

DOCUMENTATION_FORMAT: MINERAL

SAMPLE_ID: SUSTDA-20

MINERAL_TYPE: Sulfate

MINERAL: Alunite (Alunite group)

FORMULA: NaAl3(SO4)2(OH)6

FORMULA_HTML: NaAl3(SO4)2(OH)6

COLLECTION_LOCALITY: Sulfur, NV

ORIGINAL_DONOR: Ron Lyon at Stanford University

CURRENT_SAMPLE_LOCATION: USGS Denver Spectroscopy Laboratory

ULTIMATE_SAMPLE_LOCATION: USGS Denver Spectroscopy Laboratory

SAMPLE_DESCRIPTION:

The sample was sieved to the grain size interval less than 250 µm.

END_SAMPLE_DESCRIPTION.

XRD_ANALYSIS:

40 kV - 30 mA, 6.5-9.5 keV
File: alun20_mdi, *.out (smear mount on quartz plate)
References: JCPDS #41-1467; Huebner's reference patterns
Found: Natroalunite and weak, unidentified reflections at 3.33, 2.90, 1.912, 1.719, 1.606, and 1.475 angstroms

Comment: Moderately sharp and well-formed peaks suggest only moderate crystallinity and compositional heterogeneity. Some alunite peak intensities do match the relative intensities of the reference patterns.

J.S. Huebner, J. Pickrell, T. Schaefer, written communication 1994

END_XRD_ANALYSIS.

COMPOSITIONAL_ANALYSIS_TYPE: None # XRF, EM(WDS), ICP(Trace), WChem

COMPOSITION_TRACE: None

COMPOSITION_DISCUSSION:

None.

END_COMPOSITION_DISCUSSION.

MICROSCOPIC_EXAMINATION:

Pure sample. Clear elongated grains with parallel extinction along cleavage traces. Also length fast, and of low birefringence. This is all consistent with alunite.

Avg. grain size = 19µm

END_MICROSCOPIC_EXAMINATION.

SPECTROSCOPIC_DISCUSSION:

END_SPECTROSCOPIC_DISCUSSION.

SPECTRAL_PURITY: 1a2_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: splib04a r 261 0.2-3.0µm 200 g.s.= 19 µm
LIB_SPECTRA: splib05a r 817 0.2-3.0µm 200 g.s.=


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