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: 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.

IMAGE_OF_SAMPLE:
NO PHOTO

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: 1b2b3b4_ # 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.=
LIB_SPECTRA:	splib06a r 1702			g.s.=
LIB_SPECTRA:	splib06a r 1714			g.s.=