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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 GDS82 Na82 DESCRIPT

DOCUMENTATION_FORMAT: MINERAL

SAMPLE_ID: GDS82

MINERAL_TYPE: Sulfate

MINERAL: Alunite (Alunite Group)

FORMULA: (Na,K)Al3(SO4)2(OH)6

FORMULA_HTML: (Na,K)Al3(SO4)2(OH)6

COLLECTION_LOCALITY: Sadler, Texas, USA

ORIGINAL_DONOR: Roger Soffregen

CURRENT_SAMPLE_LOCATION: USGS Denver Spectroscopy Laboratory

ULTIMATE_SAMPLE_LOCATION: USGS Denver Spectroscopy Laboratory

SAMPLE_DESCRIPTION:

Low temperature diagenetic variety of alunite. May be from a lake deposit. Composition is 82 mole% Na by atomic absorption: See: Stoffregen, R., and Alpers, C., 1992, Observations on the unit-cell dimensions, H2O contents and del D values of natural and synthetic alunite: American Mineralogist, v.77, p. 1092-1098.

END_SAMPLE_DESCRIPTION.

XRD_ANALYSIS:

GDS82 Na-(82) alunite 40 kV - 30 mA, 6.5-9.5 keV (n8Oalnt.out) References: JCPDS #41-1467; Huebner's reference patterns Found: alunite, quartz, very very weak reflections at 2.38 and 1.720 A. Comment: the alunite is probably a single phase; its lattice spacing's match those of natroalunite. The alunite has sharp peaks, indicating good crystallinity and compositional homogeneity

see: Stoffregen, R., and Alpers, C., 1992, Observations on the unit-cell dimensions, H2O contents and del D values of natural and synthetic alunite: American Mineralogist, v.77, p. 1092-1098.

END_XRD_ANALYSIS.

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

COMPOSITION_TRACE: None

COMPOSITION_DISCUSSION:

Sample is a standard used by: Stoffregen, R., and Alpers, C., 1992, Observations on the unit-cell dimensions, H2O contents and del D values of natural and synthetic alunite: american Mineralogist, v.77, p. 1092-1098.

END_COMPOSITION_DISCUSSION.

MICROSCOPIC_EXAMINATION:

mode 1: 70 microns @55 vol% mode 2: 3 microns @45 vol% avg. grain size= 50 microns Larger grains have extinction characteristic of very fine grained aggregates. Cannot determine the optical properties because of small grain size. Trace opaques. Purity confirmed by XRD by: Roger Stoffregen. & G., Swayze.

END_MICROSCOPIC_EXAMINATION.

SPECTROSCOPIC_DISCUSSION:

Sample has weak vibrational features between 1.4 - 1.5, 1.76, 2.17, and 2.33 microns.

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 226 0.2-3.0µm 200 g.s.= 50µm
LIB_SPECTRA: splib05a r 281 1.3-5.3µm 200 g.s.=
LIB_SPECTRA: splib05a r 320 0.2-3.0µm 200 g.s.=


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