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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: Enstatite NMNH128288 Pyroxene DESCRIPT

DOCUMENTATION_FORMAT: MINERAL

SAMPLE_ID: NMNH128288

MINERAL_TYPE: Inosilicate

MINERAL: Enstatite (Pyroxene group)

FORMULA: Mg2Si2O6

FORMULA_HTML: Mg2Si2O6

COLLECTION_LOCALITY: Frank Smith Mine, Barkly West (near), S. Africa

ORIGINAL_DONOR: Smithsonian

CURRENT_SAMPLE_LOCATION: USGS Denver Spectroscopy Laboratory

ULTIMATE_SAMPLE_LOCATION: USGS Denver Spectroscopy Laboratory

SAMPLE_DESCRIPTION:

Forms series with Orthoferrosilite and Hypersthene. Dimorphous with Clinoenstatite.

Under the microscope this hand-picked sample appears to be moderately altered. Higher index of refraction than expected indicates probable higher iron content than pure enstatite.

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_SAMPLE_DESCRIPTION.

XRD_ANALYSIS:

Results of XRD: Enstatite plus a small amount of kaolinite and mica.

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_XRD_ANALYSIS.

COMPOSITIONAL_ANALYSIS_TYPE: EM(WDS) # XRF, EM(WDS), ICP(Trace), WChem

COMPOSITION
KEYWORD
Oxide
ASCII
Amount Weight
Percent, %
Oxide
html
COMPOSITION: SiO2 56.70 wt% SiO2
COMPOSITION: TiO2 0.01 wt% TiO2
COMPOSITION: Al2O3 1.69 wt% Al2O3
COMPOSITION: FeO 4.97 wt% FeO
COMPOSITION: MnO 0.15 wt% Mn0
COMPOSITION: MgO 35.25 wt% MgO
COMPOSITION: CaO 0.85 wt% CaO
COMPOSITION: Na2O 0.02 wt% Na2O
COMPOSITION: K2O 0.02 wt% K2O
COMPOSITION: Total 99.66 wt%
COMPOSITION: O=Cl,F,S wt%
COMPOSITION: New Total wt%

COMPOSITION_TRACE: None

COMPOSITION_DISCUSSION:

"Microprobe analysis showed some heterogenity. Six of the seven analyses were of enstatite bearing approximately 13% ferrosilite molecule. One analysis had slightly over 2% CaO, with a concomitant decrease in MgO, where the other analyses have 0.5% CaO. An average of the seven analyses is reported."

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:

Mode:
85 vol% enstatite
15 vol% mica

avg. grain size = 25 µm (other estimate gave 47µm M. Cowoski)

Straight extinction, exsolution lamellae, low order gray, biaxial, prismatic cleavage, all consistent with orthopyroxene. G. Swayze.

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 1541 0.2-3.0µm 200 g.s.= 25 µm
LIB_SPECTRA: splib05a r 2561 0.2-3.0µm 200 g.s.=


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