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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: Pyroxene HS119 DESCRIPT

DOCUMENTATION_FORMAT: MINERAL

SAMPLE_ID: HS119

MINERAL_TYPE: Inosilicate

MINERAL: Augite (Pyroxene group)

FORMULA: (Ca,Mg,Fe2+,Fe3+,Ti,Al)2(Si,Al)2O6

FORMULA_HTML: (Ca,Mg,Fe2+,Fe3+,Ti,Al)2(Si,Al)2O6

COLLECTION_LOCALITY: Oaxaca, Mexico

ORIGINAL_DONOR: Hunt and Salisbury Collection

CURRENT_SAMPLE_LOCATION: USGS Denver Spectroscopy Laboratory

ULTIMATE_SAMPLE_LOCATION: USGS Denver Spectroscopy Laboratory

SAMPLE_DESCRIPTION:

"I-4 Augite 119B-Oaxaca, Mexico. (Ca, Mg, Fe2+, Fe3+, Ti, Al)2(Si, Al)2O6: Augite is an important ferromagnesian mineral of igneous rocks, and is particularly common in basic rocks. It occurs, but less frequently, in intermediate and ultrabasic rocks. The spectrum is dominated by both Fe2+ and Fe3+ absorptions, which produce a very general broad band centered near 1.0µ. The faint bands near 2.3µ are probably due to hydroxyl combinations even though the 1.4µ band is indiscernible."

Sieve interval 74 - 250µm.

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.

END_SAMPLE_DESCRIPTION.

XRD_ANALYSIS:

40 kV - 30 mA, 7.0-9.5 keV
File: Pxn119.out, -.mdi
References: Borg and Smith (1969); Huebner's reference patterns
Found: Clinopyroxene; weak reflections at 6.5 and 3.14 angstroms; possibly significant intensity maxima at 9.4 and 8.4 angstroms.

Comment: Well crystallized pyroxene. Excellent overall match with diopside patterns, but the lattice spacings are slightly larger than in HS15.3B or endmember diopside, suggesting solid solution with hedenbergite. The relatively high background is consistent with secondary radiation due to iron. The two weak reflections are in the positions of plagioclase unindexed reflections that do not correlate with any of the pyrrhoititerace polytypes suggesting an additional phase.red orientation?

J.S.Huebner, J. Pickrell, T. Schaefer, written communication(USGS 1994)

END_XRD_ANALYSIS.

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

COMPOSITION_TRACE:

COMPOSITION_DISCUSSION:

END_COMPOSITION_DISCUSSION.

MICROSCOPIC_EXAMINATION:

Mode:
100 vol% Clinopyroxene
trace Calcite (fizz with HCl)
trace Plagioclase?

bimodal grain size:
mode 1: 270µm @ 99 vol%
mode 2: 7µm @ 1 vol%

average grain size = 270 µm Smaller grains coat 20% area large grains

Prismatic grains have two cleavages at nearly 90 deg angles, inclined extinction, slight green-blue pleochroism, 2V= 70-85 deg, biaxial (+), twinning, length slow. All these properties are consistent with this sample being a clinopyroxene (either augite, omphacite, or fassaite). 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 4092 0.2-3.0µm 200 g.s.= 270 µm
LIB_SPECTRA: splib05a r 5796 0.2-3.0µm 200 g.s.=


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