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(For further information on spectroscopy, see:
http://speclab.cr.usgs.gov)
TITLE: Almandine WS478 Garnet DESCRIPT
DOCUMENTATION_FORMAT: MINERAL
SAMPLE_ID: WS478
MINERAL_TYPE: Nesosilicate
MINERAL: Almandine (Garnet group)
FORMULA: (Fe+2)3Al2(SiO4)3
FORMULA_HTML: Fe+23Al2(SiO4)3
COLLECTION_LOCALITY: Wrangell, Alaska
ORIGINAL_DONOR: Ward Science Collection
CURRENT_SAMPLE_LOCATION: USGS Denver Spectroscopy Laboratory
ULTIMATE_SAMPLE_LOCATION: USGS Denver Spectroscopy Laboratory
SAMPLE_DESCRIPTION:
Forms series with Pyrope and with Spessartine.
IMAGE_OF_SAMPLE:
END_SAMPLE_DESCRIPTION.
XRD_ANALYSIS:
40 kV - 30 mA, 7.3- 9.5 keV
File:alma478.out,*_mdi (smear mount on quartz plate)
References: Borg and Smith (1969), JCPDS #9-427, DHZ, v. 1a (1982),
Huebner's reference patterns
Found: Garnet; weak reflection at 2.71 Angstroms.
Comment: Very sharp reflections indicate good crystallinity and suggest compositional homogeneity. Garnet unit cell range is 11.47+/-3 Angstroms indicating a pyrope-rich solid solution. The unidentified reflection is anomalously sharp (one grain?).
J.S. Huebner, J. Pickrell, T. Schaefer, written communication 1994
END_XRD_ANALYSIS.
COMPOSITIONAL_ANALYSIS_TYPE: EM # XRF, EM(WDS), ICP(Trace), WChem
| COMPOSITION KEYWORD |
Oxide ASCII |
Amount | Weight Percent, % |
Oxide html |
|---|---|---|---|---|
| COMPOSITION: | SiO2 | 39.09 | wt% | SiO2 |
| COMPOSITION: | TiO2 | 0.00 | wt% | TiO2 |
| COMPOSITION: | Al2O3 | 22.05 | wt% | Al2O3 |
| COMPOSITION: | Cr2O3 | 0.02 | wt% | Cr2O3 |
| COMPOSITION: | V2O3 | 0.01 | wt% | V2O3 |
| COMPOSITION: | FeO | 33.10 | wt% | FeO |
| COMPOSITION: | NiO | 0.01 | wt% | NiO |
| COMPOSITION: | MnO | 1.73 | wt% | MnO |
| COMPOSITION: | MgO | 5.74 | wt% | MgO |
| COMPOSITION: | CaO | 0.57 | wt% | CaO |
| COMPOSITION: | Total | 101.32 | wt% | |
| COMPOSITION: | O=Cl,F,S | wt% | #correction for Cl, F, S | |
| COMPOSITION: | New Total | 101.32 | wt% |
COMPOSITION_TRACE: None
COMPOSITION_DISCUSSION:
None
END_COMPOSITION_DISCUSSION.
MICROSCOPIC_EXAMINATION:
avg. grain size = 125µm Range = 5-325µm
Smaller grains adhere to larger ones. Trace of limonite staining and individual limonite grains. Garnet has conchoidal fractured surfaces, and is mostly isotropic under cross-polarized light. G. Swayze
END_MICROSCOPIC_EXAMINATION.
SPECTROSCOPIC_DISCUSSION:
Fe-rich composition and spectrum are consistent with this sample being almandine and not pyrope.
END_SPECTROSCOPIC_DISCUSSION.
SPECTRAL_PURITY: 1b2c3b4b # 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 183 | 0.2-3.0µm | 200 | g.s.= 125 µm |
| LIB_SPECTRA: | splib05a r 246 | 0.2-3.0µm | 200 | g.s.= |
| LIB_SPECTRA: | splib06a r 855 | g.s.= | ||
| LIB_SPECTRA: | splib06a r 867 | g.s.= |