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TITLE: Almandine HS114 Garnet DESCRIPT
MINERAL: Almandine (Garnet group)
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
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 µm; and 1.7 µm; 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 µm; confirms the presence of Fe+3 substituted for Al+3, and the suggestion of a band near 0.85µm; 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 µm;, which is quite similar to the spectrum of spessartine, with the exception of the very sharp 0.41 µm; 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.
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 un indexed 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
COMPOSITIONAL_ANALYSIS_TYPE: EM # XRF, EM(WDS), ICP(Trace), WChem
|COMPOSITION:||O=Cl,F,S||wt%||#correction for Cl, F, S|
avg. grain size = 260µm
Conchoidally fractured grains, isotropic under cross-polarized light. About 3% thin fibrous inclusions. G. Swayze
SPECTRAL_PURITY: 1b2_3_4_ # 1= 0.2-3, 2= 1.5-6, 3= 6-25, 4= 20-150 microns
|LIB_SPECTRA:||splib04a r 140||0.2-3.0µm||200||g.s.= 260 µm|
|LIB_SPECTRA:||splib05a r 194||0.2-3.0µm||200||g.s.=|
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