Sample Description USGS Spectral Library Version 7

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
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TITLE: Spessartine NMNH14143 Garnet DESCRIPT

DOCUMENTATION_FORMAT: MINERAL

SAMPLE_ID: NMNH14143

MINERAL_TYPE: Nesosilicate

MINERAL: Spessartine (Garnet group)

FORMULA: Mn3Al2(SiO4)3

FORMULA_HTML: Mn₃Al₂(SiO₄)₃

COLLECTION_LOCALITY: Rutherford #2 Mine, Amelia, Amelia County, Virginia

ORIGINAL_DONOR: National Museum of Natural History

CURRENT_SAMPLE_LOCATION: USGS Denver Spectroscopy Laboratory

ULTIMATE_SAMPLE_LOCATION: USGS Denver Spectroscopy Laboratory

SAMPLE_DESCRIPTION:

Forms series with Almandine.

"Results of petrographic examination: A group of 3mm and smaller diameter reddish crystals. Seem to be a few clear crystals adhering to the grains that were picked off; otherwise appears pure. Under petrographic microscope, sample appears pure."

Salisbury, J. W., Walter, L. W., and Vergo, N., 1987, Mid-Infrared (2.1-25µm) Spectra of Minerals: First Edition, U.S. Geological Survey Open File Report 87-263.

IMAGE_OF_SAMPLE:

END_SAMPLE_DESCRIPTION.

XRD_ANALYSIS:

Pure spessartine.

Salisbury, J. W., Walter, L. W., and Vergo, N., 1987, Mid-Infrared (2.1-25µm) Spectra of Minerals: First Edition, U.S. Geological Survey Open File Report 87-263.

Pure spessartine (Norma Vergo).

END_XRD_ANALYSIS.

COMPOSITIONAL_ANALYSIS_TYPE: EPMA # XRF, EPMA, ICP(Trace), WChem

COMPOSITION
KEYWORD Oxide
ASCII Amount Weight
Percent, % Oxide
html

COMPOSITION: SiO2 35.02 wt% SiO₂

COMPOSITION: TiO2 0.07 wt% TiO₂

COMPOSITION: Al2O3 20.74 wt% Al₂O₃

COMPOSITION: FeO 10.40 wt% FeO

COMPOSITION: MnO 30.82 wt% MnO

COMPOSITION: MgO 0.04 wt% MgO

COMPOSITION: CaO 1.61 wt% CaO

COMPOSITION: Na2O 0.09 wt% Na₂O

COMPOSITION: K2O 0.03 wt% K₂O

COMPOSITION: Total 98.81 wt%

COMPOSITION KEYWORD	Oxide ASCII	Amount	Weight Percent, %	Oxide html
COMPOSITION:	SiO2	35.02	wt%	SiO₂
COMPOSITION:	TiO2	0.07	wt%	TiO₂
COMPOSITION:	Al2O3	20.74	wt%	Al₂O₃
COMPOSITION:	FeO	10.40	wt%	FeO
COMPOSITION:	MnO	30.82	wt%	MnO
COMPOSITION:	MgO	0.04	wt%	MgO
COMPOSITION:	CaO	1.61	wt%	CaO
COMPOSITION:	Na2O	0.09	wt%	Na₂O
COMPOSITION:	K2O	0.03	wt%	K₂O
COMPOSITION:	Total	98.81	wt%

COMPOSITION_TRACE:

COMPOSITION_DISCUSSION:

Microprobe analysis found one heterogeneous area where all oxides, including silica, summed to only 27 wt% (this is probably a flaw in carbon coating). Otherwise, FeO varies from 7.5 to 12%, with inverse variation in MnO. Average of 10 analyses (other than anomalous point). Analyst: Lou Walter (done on Smithsonian microprobe using WDS?)

Salisbury, J. W., Walter, L. W., and Vergo, N., 1987, Mid-Infrared (2.1-25µm) Spectra of Minerals: First Edition, U.S. Geological Survey Open File Report 87-263.

END_COMPOSITION_DISCUSSION.

MICROSCOPIC_EXAMINATION:

END_MICROSCOPIC_EXAMINATION.

SPECTROSCOPIC_DISCUSSION:

There are weak absorptions likely from mica or other hydroxyl-bearing phase in the 2.3 micron region. G. Swayze.

END_SPECTROSCOPIC_DISCUSSION.

SPECTRAL_PURITY: 1c2c3b4b # NMNH14143 # 1= 0.2-3, 2= 1.5-6, 3= 6-25, 4= 20-150 microns