DOCUMENTATION_FORMAT: MINERAL
SAMPLE_ID: HS114
MINERAL_TYPE: Nesosilicate
MINERAL: Almandine (Garnet group)
FORMULA: (Fe+2)3Al2(SiO4)3
FORMULA_HTML: Fe+23Al2(SiO4)3
COLLECTION_LOCALITY: Warren County, New York
ORIGINAL_DONOR: Hunt and Salisbury Collection
CURRENT_SAMPLE_LOCATION: USGS Denver Spectroscopy Laboratory
ULTIMATE_SAMPLE_LOCATION: USGS Denver Spectroscopy Laboratory
SAMPLE_DESCRIPTION:
Forms series with Pyrope and with Spessartine.
"This is a common garnet of schists and gneisses and also occurs in intermediate to acidic igneous rocks. It is the most widespread variety of garnet found as a detrital mineral in sedimentary rocks. Again, this spectrum is dominated by the intense absorption at 1.28 µ and 1.7 µ due to the ferrous iron in eight-fold coordination. Also, there is a rapid fall off to the blue caused by both ferrous and ferric ion absorptions. The well defined band at 0.7 µ confirms the presence of Fe+3 substituted for Al+3, and the suggestion of a band near 0.85µ in the smallest particle size is consistent with this - even though the combination of the visible and near-infrared intense absorptions provide a well-resolved maximum near 0.85 µm, especially in the larger particle size samples. The visible spectrum shows features at 0.37, 0.43, 0.51, and 0.57 µ, which is quite similar to the spectrum of spessartine, with the exception of the very sharp 0.41 µ Mn+2 band, which is absent."
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, 7.3 -9.5 keV
File: alma114.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; very weak unindexed reflection at 2.29 angstroms
Comment: Very sharp reflections indicate excellent crystallinity
and suggest compositional homogeneity. Garnet ao=11.51+/-3 angstroms,
consistent with almandine composition (at 11.526 angstroms). Unusual rise in
background centered about 42 degrees 2 theta.
J.S. Huebner, J. Pickrell, T. Schaefer, written communication 1994
END_XRD_ANALYSIS.
COMPOSITIONAL_ANALYSIS_TYPE: EM # XRF, EM(WDS), ICP(Trace), WChem
| COMPOSITION: | SiO2 | 40.40 | wt% | SiO2 |
| COMPOSITION: | TiO2 | 0.07 | wt% | TiO2 |
| COMPOSITION: | Al2O3 | 22.97 | wt% | Al2O3 |
| COMPOSITION: | Cr2O3 | 0.01 | wt% | Cr2O3 |
| COMPOSITION: | V2O3 | 0.01 | wt% | V2O3 |
| COMPOSITION: | FeO | 22.45 | wt% | FeO |
| COMPOSITION: | NiO | 0.02 | wt% | NiO |
| COMPOSITION: | MnO | 0.53 | wt% | MnO |
| COMPOSITION: | MgO | 11.05 | wt% | MgO |
| COMPOSITION: | CaO | 4.27 | wt% | CaO |
| COMPOSITION: | Total | 101.79 | wt% | |
| COMPOSITION: | O=Cl,F,S | wt% | #correction for Cl, F, S | |
| COMPOSITION: | New Total | 101.79 | wt% |
COMPOSITION_TRACE: None
COMPOSITION_DISCUSSION:
None.
END_COMPOSITION_DISCUSSION.
MICROSCOPIC_EXAMINATION:
av gr sz = 260µm
Conchoidally fractured grains, isotropic under cross-polarized light. About 3% thin fibrous inclusions. G. Swayze
END_MICROSCOPIC_EXAMINATION.
SPECTROSCOPIC_DISCUSSION:
END_SPECTROSCOPIC_DISCUSSION.
SPECTRAL_PURITY: 1_2_3_4_
LIB_SPECTRA_HED: where Wave Range Av_Rs_Pwr Comment
LIB_SPECTRA: splib04a r 140 0.2-3.0µm 200 g.s.= 260 µm
LIB_SPECTRA: splib05a r ____ 0.2-3.0µm 200 g.s.=
LIB_SPECTRA: splib06a r ____ 1.5-25µm 250 g.s.=