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(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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