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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: Anorthite HS349 Plagioclase DESCRIPT

DOCUMENTATION_FORMAT: MINERAL

SAMPLE_ID: HS349

MINERAL_TYPE: Tectosilicate

MINERAL: Anorthite (Plagioclase, Ca end member)(Feldspar group)

FORMULA: CaAl2Si2O8

FORMULA_HTML: CaAl2Si2O8

COLLECTION_LOCALITY: Grass Valley, California

ORIGINAL_DONOR: Hunt and Salisbury Collection

CURRENT_SAMPLE_LOCATION: USGS Denver Spectroscopy Laboratory

ULTIMATE_SAMPLE_LOCATION: USGS Denver Spectroscopy Laboratory

SAMPLE_DESCRIPTION:

The original sample and vis-nir spectrum was described in:

Hunt, G.R_, J.W. Salisbury, and C.J. Lenhoff, 1973, Visible and near-infrared spectra of minerals and rocks: VI. Additional silicates. Modern Geology, v. 4, p. 85-106.

The authors reported that they removed most of the pyroxene from the original sample, and none is obvious in the visible-NIR spectrum. There are a few dark grains in the bulk sample, but << 1%. The authors also reported that original sample contained some diopside and magnetic impurities but that the magnetic impurities were removed.

Some alteration is evident by the 2.3-µm region absorption bands in the spectrum. Roger N. Clark

END_SAMPLE_DESCRIPTION.

XRD_ANALYSIS:

Anorthite + (medium) Chlorite + (small) 9.4 angstrom peak + 2.778 angstrom (Microcline?) - by Norma Vergo

Notes: the microscopic analysis shows that the impurities can't be detected, so the sample should be spectrally pure in the visible. There is a 2.3-µm band and weak 1.4 band, so some impurities do show there.

END_XRD_ANALYSIS.

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

COMPOSITION_TRACE: None

COMPOSITION_DISCUSSION:

None

END_COMPOSITION_DISCUSSION.

MICROSCOPIC_EXAMINATION:

Clean, clear to frosted rectangular grains. Very pure, no visible alteration, synthetic twining. G. Swayze

avg. grain size = 280µm

Notes: XRD indicated chlorite and others present, but they can't be detected optically, so the vis spectrum should be spectrally pure. There is a 2.3-µm band and weak 1.4 band, so some impurities do show weakly in the NIR.

END_MICROSCOPIC_EXAMINATION.

SPECTROSCOPIC_DISCUSSION:

END_SPECTROSCOPIC_DISCUSSION.

SPECTRAL_PURITY: 1c2_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 479 0.2-3.0µm 200 g.s.= 280 µm
LIB_SPECTRA: splib05a r 1099 0.2-3.0µm 200 g.s.=


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