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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 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:
Photo 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, EPMA, 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