U.S. Geological Survey home page

USGS Spectral Library Version 7 Sample Description

Kokaly, R.F., Clark, R.N., Swayze, G.A., Livo, K.E., Hoefen, T.M., Pearson, N.C., Wise, R.A., Benzel, W.M., Lowers, H.A., Driscoll, R.L., and Klein, A.J., 2017, USGS Spectral Library Version 7: U.S. Geological Survey Data Series 1035, 61 p., https://doi.org/10.3133/ds1035
For more information on the library, see: local link web link

TITLE: Almandine HS114 Garnet DESCRIPT

DOCUMENTATION_FORMAT: MINERAL

SAMPLE_ID: HS114.1B, HS114.2B, HS114.3B, HS114.4B, HS114.6

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 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.

Grain size fractions are indicated by the extension after the sample number:
.1B = <5 µm
.2B = <74 µm
.3B = 74-250 µm
.4B = 250-1200 µm
.6 = cut slab

IMAGE_OF_SAMPLE:
Photo of sample

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 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

END_XRD_ANALYSIS.

COMPOSITIONAL_ANALYSIS_TYPE: EM # XRF, EPMA, ICP(Trace), WChem

TD>SiO2
COMPOSITION
KEYWORD
Oxide
ASCII
Amount Weight
Percent, %
Oxide
html
COMPOSITION: SiO2 40.40 wt%
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:

avg. grain size = 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: 1b2_3_4_ # HS114.1B # 1= 0.2-3, 2= 1.5-6, 3= 6-25, 4= 20-150 microns
SPECTRAL_PURITY: 1b2_3_4_ # HS114.2B # 1= 0.2-3, 2= 1.5-6, 3= 6-25, 4= 20-150 microns
SPECTRAL_PURITY: 1b2b3b4_ # HS114.3B # 1= 0.2-3, 2= 1.5-6, 3= 6-25, 4= 20-150 microns
SPECTRAL_PURITY: 1b2_3_4_ # HS114.4B # 1= 0.2-3, 2= 1.5-6, 3= 6-25, 4= 20-150 microns
SPECTRAL_PURITY: 1b2_3_4_ # HS114.6 # 1= 0.2-3, 2= 1.5-6, 3= 6-25, 4= 20-150 microns