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USGS Spectral Library Version 7 Sample Description

Kokaly, R.F., Clark, R.N., Swayze, G.A., Livo, K.E., Hoefen, T.M., Pearson, N.C., Wise, R.A., Benzel, W.M., Lowers, H.A., Driscoll, R.L., and Klein, A.J., 2017, USGS Spectral Library Version 7: U.S. Geological Survey Data Series 1035, 61 p., https://doi.org/10.3133/ds1035
For more information on the library, see: local link web link

TITLE: Anorthite HS201 Plagio DESCRIPT

DOCUMENTATION_FORMAT: MINERAL

SAMPLE_ID: HS349.1B, HS349.2B, HS349.3B, HS349.4B

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

Grain size fractions are indicated by the extension after the sample number:
.1B = <5 µm
.2B = <74 µm
.3B = 74-250 µm
.4B = 250-1200 µm

IMAGE_OF_SAMPLE:
Photo of sample

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, EPMA, 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_ # HS349.1B # 1= 0.2-3, 2= 1.5-6, 3= 6-25, 4= 20-150 microns
SPECTRAL_PURITY: 1c2_3_4_ # HS349.2B # 1= 0.2-3, 2= 1.5-6, 3= 6-25, 4= 20-150 microns
SPECTRAL_PURITY: 1c2c3c4c # HS349.3B # 1= 0.2-3, 2= 1.5-6, 3= 6-25, 4= 20-150 microns
SPECTRAL_PURITY: 1c2_3_4_ # HS349.4B # 1= 0.2-3, 2= 1.5-6, 3= 6-25, 4= 20-150 microns